Spinal cord stimulation system without paresthesia

Abstract

Spinal cord stimulation systems without paresthesia are disclosed. Ultimately, sub-perception (no paresthesia) therapy is used for patient therapy. However, super-perception stimulation is used during a "sweet spot search" to select the active electrodes for the patient. This allows the sweet spot search to occur much more quickly and does not require wash-in of the various electrode combinations tried. After the electrodes are selected using super-perception therapy, the selected electrodes are used to titrate the therapy to a sub-perception level. This sub-perception therapy has been studied using pulses at or below 10 kHz, and a statistically significant correlation has been determined between pulse width (PW) and frequency (F) within the frequency range that SCS patients experience significant reduction in symptoms such as back pain. Advantageously, sub-perception stimulation at such low frequencies significantly reduces power consumption in the patient's neurostimulator.

Description

[0001] This application is a continuation of patent application number “201880066175.9” filed on “10 August 2018” and titled “Spinal Cord Stimulation System Without Paresthesia”. TECHNICAL FIELD

[0002] The present application relates to implantable medical devices (IMDs), generally to spinal cord stimulators, and more particularly to methods of controlling such devices. BACKGROUND

[0003] Implantable neurostimulator devices are devices that generate and deliver electrical stimuli to bodies' nerves and tissues for the therapy of various biological disorders, such as pacemakers to treat heart rhythm disorders, defibrillators to treat cardiac fibrillation, cochlear stimulators to treat deafness, retinal stimulators to treat blindness, muscle stimulators to produce coordinated limb movements, spinal cord stimulators to treat chronic pain, cortical and deep brain stimulators to treat movement and psychological disorders, and other neural stimulators to treat urinary incontinence, sleep apnea, shoulder subluxation, etc. The following description will generally focus on the use of the present application within a Spinal Cord Stimulation (SCS) system, such as disclosed in U.S. Patent 6,516,227. However, the present application can find applicability in any implantable neurostimulator device system.

[0004] SCS systems generally include an implantable pulse generator (IPG) 10 shown in Figure 1 FIG. 1. The IPG 10 includes a biocompatible device housing 12 that houses the circuitry and battery 14 required for IPG operation. The IPG 10 is coupled to electrodes 16 via one or more electrode lead 15 that form an electrode array 17. The electrodes 16 are configured to contact the patient's tissue and are carried on a flexible body 18 that also houses a separate lead 20 coupled to each electrode 16. The lead 20 is also coupled to a proximal contact 22 that can be inserted into a lead connector 24 secured within a header 23 on the IPG 10, which can include, for example, epoxy. Once inserted, the proximal contact 22 connects to a header contact within the lead connector 24, which in turn is coupled by a feedthrough pin through a housing feedthrough to the circuitry within the housing 12, although these details are not shown.

[0005] In the illustrated IPG 10, there are sixteen lead electrodes (El through E16) split between two lead wires 15, with the header 23 containing a 2x1 array of lead connectors 24. However, the number of lead wires and electrodes in an IPG is application-specific and thus can vary. The conductive housing 12 can also include an electrode (Ec). In SCS applications, the electrode leads 15 are typically implanted in the patient's spinal column near the dura on both sides of the spinal cord midline. The proximal electrodes 22 tunnel through the patient's tissue to a distant point such as the buttock where the IPG housing 12 is implanted, at which point they are coupled to the lead connectors 24. In other IPG examples designed for direct implantation at the site requiring stimulation, the IPG can be leadless, with the sixteen electrodes instead appearing on the body of the IPG for contacting the patient's tissue. The IPG lead 15 can be integrated with and permanently connected to the housing 12 in other IPG schemes. The purpose of SCS therapy is to provide electrical stimulation from the electrodes 16 to alleviate the patient's symptoms, most notably chronic back pain.

[0006] The IPG 10 can include an antenna 26a that allows it to communicate bidirectionally with a plurality of external devices, as shown in Figure 4 . The antenna 26a depicted in Figure 1 is shown as a conductive coil within the housing 12, although the coil 26a can also appear in the header 23. When the antenna 26a is configured as a coil, communication with external devices preferably occurs using near-field magnetic induction. The IPG can also include a radio frequency (RF) antenna 26b. In Figure 1 , the RF antenna 26b is shown within the header 23, although it can also be within the housing 12. The RF antenna 26b can include a patch, slot, or wire, and can operate as a monopole or a dipole. The RF antenna 26b preferably communicates using far-field electromagnetic waves. The RF antenna 26b can operate according to any number of known RF communication standards, such as Bluetooth, Zigbee, WiFi, and MICS, among others.

[0007] Stimulation in the IPG 10 is typically provided by pulses, as shown in Figure 2 . Stimulation parameters typically include: the amplitude (A; whether current or voltage) of the pulses; the frequency (F) and pulse width (PW) of the pulses; the electrodes 16 (E) that are activated to provide such stimulation; and the polarity (P) of such activated electrodes, i.e., whether the activated electrodes act as anodes (sources of current to the tissue) or cathodes (sinks of current from the tissue). These stimulation parameters, taken together, comprise a stimulation program that the IPG 10 can execute to provide therapeutic stimulation to the patient.

[0008] In Figure 2In the example, electrode E5 has been selected as the anode, and thus provides a pulse that generates a positive current of amplitude +A to the tissue. Electrode E4 has been selected as the cathode, and thus provides a pulse that absorbs a corresponding negative current of amplitude -A from the tissue. This is an example of bipolar stimulation, in which only two lead-based electrodes (one anode and one cathode) are used to provide stimulation to the tissue. However, more than one electrode can act as the anode at a given time, and more than one electrode can act as the cathode at a given time (e.g., tripolar stimulation, tetrapolar stimulation, etc.).

[0009] like Figure 2 The pulses shown are biphasic, comprising a first phase 30a followed by a second phase 30b of opposite polarity. The use of biphasic pulses is well known for its ability to facilitate effective charge recovery. For example, the current path to each electrode in the tissue may include a series-connected DC blocking capacitor, see, for example, U.S. Patent Application Publication 2016 / 0144183, which will be charged during the first phase 30a and discharged (recovered) during the second phase 30b. In the example shown, the first phase 30a and the second phase 30b have the same duration and amplitude (although opposite polarities), ensuring the same amount of charge during both phases. However, the second phase 30b can also be charged in balance with the first phase 30a if the integrals of the amplitude and duration of the two phases are equal in magnitude, as is well known. The pulse width PW is defined herein as the duration of the first pulse phase 30a, although the pulse width may also refer to the total duration of the first pulse phase 30a and the second pulse phase 30b. Note that an interphase period (IP) may be provided between the two phases 30a and 30b, during which no stimulation is provided.

[0010] The IPG 10 includes a stimulation circuit 28, which can be programmed to generate stimulation pulses at electrodes according to a stimulation program. The stimulation circuit 28 may include, for example, circuits described in U.S. Provisional Patent Applications Serial Nos. 62 / 386,000 and 62 / 393,003, both filed September 10, 2016, or USP 8,606,362 and 8,620,436.

[0011] Figure 3An external trial stimulation environment is shown that can precede implantation of IPG 10 into a patient. During external trial stimulation, stimulation of the intended implanted patient can be attempted without the commitment of implanting IPG 10. In contrast, one or more trial leads 15' are implanted in the patient's tissue 32 at target locations 34, such as within the spinal column as previously described. The proximal ends of the one or more trial leads 15' exit an incision 36 and are connected to an external trial stimulator (ETS) 40. ETS 40 generally mimics the operation of IPG 10, and thus can provide stimulation pulses to the patient's tissue as described above. See, e.g., 9,259,574, which discloses a design for an ETS. ETS 40 is generally worn externally by the patient for a short period of time (e.g., two weeks), which allows the patient and his clinician to experiment with different stimulation parameters to attempt and find a stimulation program that alleviates the patient's symptoms (e.g., pain). If the external trial stimulation proves successful, the one or more trial leads 15' are removed, and IPG 10 and one or more leads 15 are implanted as described above; if not, only the one or more trial leads 15' are removed.

[0012] Like IPG 10, ETS 40 can include one or more antennas capable of bidirectional communication with external devices, as described above with respect to Figure 4 Further explanation. Such antennas can include a near-field magnetic induction coil antenna 42a, and / or a far-field RF antenna 42b, as previously described. ETS 40 can also include stimulation circuitry 44 capable of forming stimulation pulses according to a stimulation program, which can be similar to or include the same stimulation circuitry 28 present in IPG 10. ETS 40 can also include a battery (not shown) for operating power.

[0013] Figure 4 Various external devices are shown that can wirelessly communicate data with IPG 10 and ETS 40, including a patient's handheld external controller 45 and a clinician programmer 50. Both devices 45 and 50 can be used to send a stimulation program to IPG 10 or ETS 40— i.e., to program their stimulation circuitry 28 and 44 to generate pulses of the previously described shapes and timing. Both devices 45 and 50 can also be used to adjust one or more stimulation parameters of a stimulation program that IPG 10 or ETS 40 is currently executing. Devices 45 and 50 can also receive information from IPG 10 or ETS 40, such as various status information, etc.

[0014] External controller 45 can be as described, for example, in U.S. Patent Application Publication 2015 / 0080982, and can include any specialized controller configured to work with IPG 10. External controller 45 can also include a general purpose mobile electronic device such as a mobile phone that has been programmed with a medical device application (MDA) that allows it to function as a wireless controller for IPG 10 or ETS 40, as described in U.S. Patent Application Publication 2015 / 0231402. External controller 45 includes a user interface that includes means for inputting commands (e.g., buttons or icons) and a display 46. The user interface of external controller 45 enables a patient to adjust stimulation parameters, although it can have limited functionality when compared to more powerful clinician programmer 50, described later.

[0015] External controller 45 can have one or more antennas capable of communicating with IPG 10 and ETS 40. For example, external controller 45 can have a near-field magnetic induction coil antenna 47a capable of wireless communication with coil antenna 26a or 42a in IPG 10 or ETS 40. External controller 45 can also have a far-field RF antenna 47b capable of wireless communication with RF antenna 26b or 42b in IPG 10 or ETS 40.

[0016] External controller 45 can also have control circuitry 48, such as a microprocessor, microcomputer, FPGA, other digital logic structure capable of executing instructions of an electronic device, etc. Control circuitry 48 can, for example, receive patient adjustments to stimulation parameters and create a stimulation program to be wirelessly transmitted to IPG 10 or ETS 40.

[0017] Clinician programmer 50 is further described in U.S. Patent Application Publication 2015 / 0360038, and is only briefly described here. Clinician programmer 50 can include a computing device 51, such as a desktop, laptop, notebook, tablet, mobile smart phone, personal digital assistant (PDA) type mobile computing device, etc. In Figure 4 In particular, computing device 51 is shown as a portable computer that includes typical computer user interface means, such as a screen 52, mouse, keyboard, speakers, stylus, printer, etc., not all of which are shown for convenience. Also shown in Figure 4 Also shown in is an accessory device for clinician programmer 50 that is generally specific to its operation as a stimulation controller, such as a communication "wand" 54, and a joystick 58, which can be coupled to an appropriate port on computing device 51, such as, for example, a USB port 59.

[0018] The antenna in clinician programmer 50 for communicating with IPG 10 or ETS 40 can depend on the type of antenna included in those devices. If the patient's IPG 10 or ETS 40 includes a coil antenna 26a or 42a, then wand 54 can likewise include a coil antenna 56a for establishing near-field magnetic induction communication at close range. In this example, wand 54 can be secured in close proximity to the patient, such as by placing wand 54 in a belt or holster that can be worn by the patient and is in the vicinity of the patient's IPG 10 or ETS 40.

[0019] If IPG 10 or ETS 40 includes an RF antenna 26b or 42b, then wand 54, computing device 41, or both can likewise include an RF antenna 56b to establish communication with IPG 10 or ETS 40 at a more distant range. (Wand 54 can not be necessary in this case). Clinician programmer 50 can also establish communication with other devices and networks, such as the Internet, wirelessly or via a wired link provided at an Ethernet or network port.

[0020] To program the stimulation programs or parameters of IPG 10 or ETS 40, the clinician interfaces with a clinician programmer graphical user interface (GUI) 64 provided on display 52 of computing device 51. As will be understood by those skilled in the art, GUI 64 can be presented by executing clinician programmer software 66 on computing device 51, which can be stored on non-volatile memory 68 of the device. Those skilled in the art will also appreciate that execution of clinician programmer software 66 in computing device 51 can be facilitated by control circuitry 70, such as a microprocessor, microcomputer, FPGA, other digital logic structure capable of executing programs in a computing device, etc. Such control circuitry 70, in addition to executing clinician programmer software 66 and presenting GUI 64, can also implement communication via antenna 56a or 56b to transfer selected stimulation parameters to the patient's IPG 10 through GUI 64.

[0021] A portion of GUI 64 is shown in one example in Figure 5 Those skilled in the art will understand that the details of GUI 64 will depend on where the clinician programmer software 66 is in its execution, which will depend on the GUI selections that the clinician has already made. Figure 5A GUI 64 is shown at a point to allow stimulation parameters to be set for a patient and stored as a stimulation program. Shown on the left is a program interface 72 which allows stimulation programs to be named, loaded and saved for a patient as further explained in the '038 publication. Shown on the right is a stimulation parameter interface 82 in which the specified stimulation parameters (A, D, F, E, P) can be defined for a stimulation program. Values for stimulation parameters related to the waveform shape (A; in this example, current), pulse width (PW) and frequency (F) are shown in a waveform parameter interface 84 which includes buttons that a clinician can use to increase or decrease these values.

[0022] Stimulation parameters related to the electrodes 16 (the electrodes E that are activated and their polarity P) can be adjusted in an electrode parameter interface 86. The electrode stimulation parameters are also visible and can be manipulated in a lead interface 92 which shows the leads 15 (or 15') in their approximate positions relative to each other, e.g., on the left or right side of the spinal column. A cursor 94 (or other selection device such as a mouse pointer) can be used to select a particular electrode in the lead interface 92. Buttons in the electrode parameter interface 86 allow the selected electrode (including the case electrode Ec) to be designated as an anode, a cathode or off. The electrode parameter interface 86 also allows the relative strength of the anode current or cathode current for the selected electrode to be specified in percentage X. This is particularly useful if more than one electrode is acting as an anode or cathode at a given time, as explained in the '038 publication. According to the example waveform shown in FIG. 6 of the '038 publication, electrode E5 has been selected as the only anode to produce current, and this electrode receives the specified anode current +A at X = 100%. Likewise, electrode E4 has been selected as the only cathode to absorb current, and this electrode receives the specified cathode current -A at X = 100%. Figure 2

[0023] ​The GUI 64 as shown specifies a pulse width PW for only the first pulse phase 30a. The clinician programmer software 66 running and receiving input from the GUI 64 will still ensure that the IPG 10 and ETS 40 are programmed to present the stimulation program as biphasic pulses when biphasic pulses are to be used. For example, the clinician programmer software 66 can automatically determine the duration and amplitude of both pulse phases 30a and 30b (e.g., each having a duration of PW and having opposite polarities +A and -A). The advanced menu 88 can also be used to define the relative duration and amplitude of pulse phases 30a and 30b, among other things, and allow other more advanced modifications, such as setting the duty cycle (on / off time) of the stimulation pulses, and the rise time over which the stimulation reaches its programmed amplitude (A), etc. The mode menu 90 allows the clinician to select different modes for determining the stimulation parameters. For example, the mode menu 90 can be used to implement electronic trolling, which includes an automatic programming mode that performs current steering along the electrode array by moving the cathode in a bipolar fashion, as described in the '038 publication.

[0024] While the GUI 64 is shown as operating in the clinician programmer 50, the user interface of the external controller 45 can also provide similar functionality. SUMMARY

[0025] In a first example, a method for programming a spinal cord stimulator having a plurality of electrodes including an array can include programming the spinal cord stimulator implanted in a patient to generate a stimulation pulse including a shape of a frequency and a pulse width to at least two electrodes of the plurality of electrodes, where the frequency and the pulse width are selected based on information related to a frequency and a pulse width at which the stimulation pulse is to be formed to provide pain relief to the patient without paresthesia.

[0026] The stimulation pulse can form a bipolar in tissue of the patient. The spinal cord stimulator can be programmed to generate the stimulation pulse to at least three electrodes of the plurality of electrodes to form a virtual bipolar in tissue of the patient.

[0027] The spinal cord stimulator can also include a control circuit, where the information is stored in the control circuit. The frequency can be provided to the control circuit, and the information can be used to determine the pulse width. The pulse width can be provided to the control circuit, and the information can be used to determine the frequency. The information can be stored in a control circuit of an external device used to program the spinal cord stimulator. The control circuit can use the information to determine at least one of the frequency or the pulse width at which to form stimulation pulses to provide pain relief without paresthesia, and the control circuit also wirelessly transmits the at least one of the frequency or the pulse width to the spinal cord stimulator. The information can be used to select the frequency and the pulse width that require the lowest amount of power for the stimulation pulses.

[0028] Each of the stimulation pulses can include a biphasic pulse having a first phase with a first polarity and a second phase with a second polarity opposite the first polarity, where the first phase and the second phase are actively driven by stimulation circuitry in the spinal cord stimulator. Each of the stimulation pulses can include a symmetric biphasic pulse, where a duration of the first phase is equal to a duration of the second phase, and where an amplitude of the first phase is equal to an amplitude of the second phase but has an opposite polarity to the amplitude of the second phase. The pulse width can include (i) a total duration of the first phase and the second phase, or (ii) a duration of the first phase or the second phase.

[0029] The frequency can be 1 kHz, or less than 1 kHz. The frequency and the pulse width at which to form stimulation pulses to provide pain relief without paresthesia are above or within a linearly defined region defined by the following points:

[0030] (10 Hz, 265 μs), (10 Hz, 435 μs), (50 Hz, 370 μs), and (50 Hz, 230 μs),

[0031] (50 Hz, 230 μs), (50 Hz, 370 μs), (100 Hz, 325 μs), and (100 Hz, 195 μs),

[0032] (100 Hz, 195 μs), (100 Hz, 325 μs), (200 Hz, 260 μs), and (200 Hz, 160 μs),

[0033] (200 Hz, 160 μs), (200 Hz, 260 μs), (400 Hz, 225 μs), and (400 Hz, 140 μs),

[0034] (400 Hz, 140 μs), (400 Hz, 225 μs), (600 Hz, 200 μs), and (600 Hz, 120 μs),

[0035] (600Hz, 120μs), (600Hz, 200μs), (800Hz, 175μs) and (800Hz, 105μs), or

[0036] (800Hz, 105μs), (800Hz, 175μs), (1000Hz, 150μs) and (1000Hz, 90μs). The frequencies and pulse widths at which the stimulus pulses are formed to provide pain relief without paresthesia do not include a duty cycle associated with a constant frequency and pulse width below 1 kHz.

[0037] The frequencies can be in the range 1 kHz to 10 kHz. The frequencies and pulse widths at which the stimulus pulses are formed to provide pain relief without paresthesia are above or within one or more linearly defined regions defined by:

[0038] (i) (1 kHz, 98.3μs), (1 kHz, 109μs), (4 kHz, 71.4μs) and (4 kHz, 64.6μs); or (ii) (4 kHz, 71.4μs), (4 kHz, 64.6μs), (7 kHz, 44.2μs) and (7 kHz, 48.8μs); or

[0039] (iii) (7 kHz, 44.2μs), (7 kHz, 48.8μs), (10 kHz, 29.9μs) and (10 kHz, 27.1μs).

[0040] or

[0041] (i) (1 kHz, 96.3μs), (1 kHz, 112μs), (4 kHz, 73.8μs) and (4 kHz, 62.2μs); or (ii) (4 kHz, 73.8μs), (4 kHz, 62.2μs), (7 kHz, 43.6μs) and (7 kHz, 49.4μs); or

[0042] (iii) (7 kHz, 43.6μs), (7 kHz, 49.4μs), (10 kHz, 30.0μs) and (10 kHz, 27.0μs).

[0043] or

[0044] (i) (1 kHz, 69.6μs), (1 kHz, 138.4μs), (4 kHz, 93.9μs) and (4 kHz, 42.1μs); or

[0045] (ii) (4kHz, 93.9μs), (4kHz, 42.1μs), (7kHz, 33.4μs) and (7kHz, 59.6μs); or

[0046] (iii) (7kHz, 33.4μs), (7kHz, 59.6μs), (10kHz, 35.2μs) and (10kHz, 21.8μs).

[0047] or

[0048] (i) (1kHz, 50.0μs), (1kHz, 200.0μs), (4kHz, 110.0μs) and (4kHz, 30.0μs); or

[0049] (ii) (4kHz, 110.0μs), (4kHz, 30.0μs), (7kHz, 30.0μs) and (7kHz, 60.0μs); or

[0050] (iii) (7kHz, 30.0μs), (7kHz, 60.0μs), (10kHz, 40.0μs) and (10kHz, 20.0μs).

[0051] The method may further include directing current between multiple electrodes to adjust the position at which a stimulation pulse is applied to the patient. The method may also include adjusting the amplitude of the stimulation pulse based on the adjusted position at which the stimulation pulse is applied to the patient.

[0052] The frequency, pulse width, and amplitude may include three of a set of stimulation parameters used to generate the stimulation pulse, and the method may further include, in response to an instruction, reducing at least one of the stimulation parameters by an amount or percentage, or reducing at least one of the stimulation parameters by an amount or percentage. The stimulation circuit may, in response to an instruction, reduce the amplitude of the stimulation pulse by an amount or percentage, or reduce the amplitude of the stimulation pulse by an amount or percentage.

[0053] The frequency and pulse width may include two stimulation parameters used to generate a set of stimulation pulses, and the method may further include adjusting at least one of the stimulation parameters in response to changes in the patient's position or activity. The spinal stimulator can be programmed during a programming session, and the stimulation pulses can be washed in over a period of one hour or less during the programming session to provide pain relief to the patient without sensory abnormalities.

[0054] In a second example, a system is disclosed that can include a spinal cord stimulator including stimulation circuitry programmed to generate stimulation pulses including a shape of a frequency and a pulse width to at least one of a plurality of electrodes, where the frequency and the pulse width are selected based on information related to a frequency and a pulse width at which to form stimulation pulses to provide pain relief without paresthesia.

[0055] The stimulation pulses can be configured to form a bipolar in tissue of the patient. The stimulation circuitry can be programmed to generate the stimulation pulses to at least three of the plurality of electrodes to form a virtual bipolar in tissue of the patient. The spinal cord stimulator can further include control circuitry, where the information is stored in the control circuitry. The frequency can be provided to the control circuitry and the pulse width can be determined using the information. The pulse width can be provided to the control circuitry and the frequency can be determined using the information.

[0056] The system can further include an external device including control circuitry, where the information is stored in the control circuitry. The control circuitry can be configured to determine at least one of a frequency or a pulse width at which to form stimulation pulses to provide pain relief without paresthesia using the information, and where the control circuitry is further configured to wirelessly transmit the at least one of the frequency or the pulse width to the spinal cord stimulator.

[0057] The frequency and the pulse width are selected using the information to be a frequency and a pulse width that require a lowest amount of power for the stimulation pulses.

[0058] Each of the stimulation pulses can include a biphasic pulse having a first phase having a first polarity and a second phase having a second polarity opposite the first polarity, where the first phase and the second phase are actively driven by the stimulation circuitry in the spinal cord stimulator. Each of the stimulation pulses can include a symmetric biphasic pulse, where a duration of the first phase is equal to a duration of the second phase, and where an amplitude of the first phase is equal to an amplitude of the second phase but has an opposite polarity to the amplitude of the second phase. The pulse width can include (i) a total duration of the first phase and the second phase, or (ii) a duration of the first phase or the second phase.

[0059] The frequency can be 1 kHz or below 1 kHz. The frequency and the pulse width at which to form stimulation pulses to provide pain relief without paresthesia are defined by above or within a linearly bounded region defined by the following points:

[0060] (10 Hz, 265 μs), (10 Hz, 435 μs), (50 Hz, 370 μs) and (50 Hz, 230 μs), (50 Hz, 230 μs), (50 Hz, 370 μs), (100 Hz, 325 μs) and (100 Hz, 195 μs), (100 Hz, 195 μs), (100 Hz, 325 μs), (200 Hz, 260 μs) and (200 Hz, 160 μs), (200 Hz, 160 μs), (200 Hz, 260 μs), (400 Hz, 225 μs) and (400 Hz, 140 μs), (400 Hz, 140 μs), (400 Hz, 225 μs), (600 Hz, 200 μs) and (600 Hz, 120 μs), (600 Hz, 120 μs), (600 Hz, 200 μs), (800 Hz, 175 μs) and (800 Hz, 105 μs), or

[0061] (800 Hz, 105 μs), (800 Hz, 175 μs), (1000 Hz, 150 μs) and (1000 Hz, 90 μs).

[0062] The frequency and pulse width at which the stimulus pulses are formed to provide pain relief without paresthesia do not include a duty cycle associated with a frequency and pulse width constant in the range of 10 Hz to 1 kHz.

[0063] The frequency can be in the range of 1 kHz to 10 kHz. The frequency and pulse width at which the stimulus pulses are formed to provide pain relief without paresthesia are above or within one or more linearly defined regions defined by the following points:

[0064] (i) (1 kHz, 98.3 μs), (1 kHz, 109 μs), (4 kHz, 71.4 μs) and (4 kHz, 64.6 μs); or (ii) (4 kHz, 71.4 μs), (4 kHz, 64.6 μs), (7 kHz, 44.2 μs) and (7 kHz, 48.8 μs); or

[0065] (iii) (7 kHz, 44.2 μs), (7 kHz, 48.8 μs), (10 kHz, 29.9 μs) and (10 kHz, 27.1 μs).

[0066] or

[0067] (i) (1kHz, 96.3μs), (1kHz, 112μs), (4kHz, 73.8μs), and (4kHz, 62.2μs); or (ii) (4kHz, 73.8μs), (4kHz, 62.2μs), (7kHz, 43.6μs), and (7kHz, 49.4μs); or

[0068] (iii) (7kHz, 43.6μs), (7kHz, 49.4μs), (10kHz, 30.0μs) and (10kHz, 27.0μs).

[0069] or

[0070] (i) (1kHz, 69.6μs), (1kHz, 138.4μs), (4kHz, 93.9μs), and (4kHz, 42.1μs); or

[0071] (ii) (4kHz, 93.9μs), (4kHz, 42.1μs), (7kHz, 33.4μs) and (7kHz, 59.6μs); or

[0072] (iii) (7kHz, 33.4μs), (7kHz, 59.6μs), (10kHz, 35.2μs) and (10kHz, 21.8μs).

[0073] or

[0074] (i) (1kHz, 50.0μs), (1kHz, 200.0μs), (4kHz, 110.0μs) and (4kHz, 30.0μs); or

[0075] (ii) (4kHz, 110.0μs), (4kHz, 30.0μs), (7kHz, 30.0μs) and (7kHz, 60.0μs); or

[0076] (iii) (7kHz, 30.0μs), (7kHz, 60.0μs), (10kHz, 40.0μs) and (10kHz, 20.0μs).

[0077] The stimulation circuit can be configured to direct current between multiple electrodes to adjust the position at which a stimulation pulse is applied to the patient. The stimulation circuit can also be configured to adjust the amplitude of the stimulation pulse based on the adjusted position at which the stimulation pulse is applied to the patient.

[0078] The frequency, pulse width, and amplitude can comprise three of a set of stimulation parameters used to generate a set of stimulation pulses, wherein the stimulation circuit can be configured to decrease at least one of the stimulation parameters by an amount or percentage or decrease at least one of the stimulation parameters by an amount or percentage in response to the instruction.

[0079] The frequency and pulse width can comprise two of a set of stimulation parameters used to generate a set of stimulation pulses, and wherein the stimulation circuit can be configured to adjust at least one of the stimulation parameters in response to a change in the patient's position or activity.

[0080] The spinal cord stimulator can be configured to be programmable during a programming session, and wherein the spinal cord stimulator is configured to wash in stimulation pulses during an hour or less of the programming session to provide pain relief to the patient without paresthesia.

[0081] In a third example, a method for programming a spinal cord stimulator having a plurality of electrodes comprising an array is disclosed, which can include: (a) providing a plurality of different first sets of stimulation parameters to the spinal cord stimulator, wherein each first set of stimulation parameters causes the spinal cord stimulator to form a biphasic test pulse at at least two of the electrodes, wherein each biphasic test pulse comprises a first phase having a first polarity and a second phase having a second polarity opposite the first polarity, wherein the first pulse phase and the second pulse phase are both actively driven by a stimulation circuit in the spinal cord stimulator, and wherein each first set of stimulation parameters causes suprathreshold stimulation to occur at a different location relative to the array; (b) determining a first set of stimulation parameters that treats a patient's painful symptoms, the determined first set of stimulation parameters corresponding to a treatment location relative to the array; and (c) providing a second set of stimulation parameters to the spinal cord stimulator for causing the spinal cord stimulator to form a treatment pulse at at least two of the electrodes, wherein the second set of stimulation parameters causes subthreshold stimulation to occur at the treatment location.

[0082] The biphasic test pulse is formed at 130 Hz or less. The charge of the first phase can be equal to the charge of the second phase. The duration of the first phase can be different than the duration of the second phase, and the amplitude of the first phase can be different than the amplitude of the second phase. The biphasic test pulse can comprise a symmetrical biphasic pulse, wherein the duration of the first phase is equal to the duration of the second phase, and wherein the amplitude of the first phase is equal to the amplitude of the second phase but has a polarity opposite the amplitude of the second phase. The charge of the first phase can not be equal to the charge of the second phase.

[0083] The treatment pulses can include biphasic pulses having a first phase having a first polarity and a second phase having a second polarity opposite the first polarity. The treatment pulses can include symmetric biphasic pulses in which a duration of the first phase is equal to a duration of the second phase and in which an amplitude of the first phase is equal to an amplitude of the second phase but has an opposite polarity to the amplitude of the second phase.

[0084] The second set of stimulation parameters can be determined by adjusting at least one of the stimulation parameters of the determined first set of stimulation parameters without adjusting the stimulation locations relative to the array. The determined first set of stimulation parameters can include a set of stimulation parameters with which the patient responds favorably to treatment of the pain symptoms.

[0085] Each of the first set of stimulation parameters can cause suprathreshold stimulation to occur as a multipole at different locations. At least some or all of the first set of stimulation parameters can cause suprathreshold stimulation to occur as a bipolar at different locations. At least some of the first set of stimulation parameters can cause suprathreshold stimulation to occur as a virtual bipolar at different locations. The second stimulation parameters can cause subthreshold stimulation to occur as a multipole at the treatment location. The second stimulation parameters can cause subthreshold stimulation to occur as a bipolar at the treatment location. The second stimulation parameters can cause subthreshold stimulation to occur as a virtual bipolar at the treatment location.

[0086] The determined first set of stimulation parameters can be determined by using feedback from the patient. The determined first set of stimulation parameters can include an amplitude of a test pulse and wherein the second set of stimulation parameters includes an amplitude of a treatment pulse and wherein the amplitude of the treatment pulse is lower than the amplitude of the test pulse. The determined first set of stimulation parameters can differ from the second set of stimulation parameters in only the amplitude of the test pulse and the treatment pulse.

[0087] Each of the first set of stimulation parameters and the second set of stimulation parameters can include an indication of which of at least two electrodes is active, an indication of a polarity of the at least two electrodes, and an indication of an amplitude of a current at the at least two electrodes.

[0088] The second set of stimulation parameters can include a frequency and a pulse width of the treatment pulses, wherein the frequency is 10 kHz or lower and at least one of the frequency and the pulse width is selected to cause subthreshold stimulation to occur. The selected frequency and pulse width can be above or within one or more linearly defined regions defined by the following points:

[0089] (i) (10 Hz, 265 μβ), (10 Hz, 435 μβ), (50 Hz, 370 μβ), and (50 Hz, 230 μβ); or

[0090] (ii) (50Hz, 230μs), (50Hz, 370μs), (100Hz, 325μs) and (100Hz, 195μs); or

[0091] (iii) (100Hz, 195μs), (100Hz, 325μs), (200Hz, 260μs) and (200Hz, 160μs); or

[0092] (iv) (200Hz, 160μs), (200Hz, 260μs), (400Hz, 225μs) and (400Hz, 140μs); or

[0093] (v) (400Hz, 140μs), (400Hz, 225μs), (600Hz, 200μs) and (600Hz, 120μs); or

[0094] (vi) (600Hz, 120μs), (600Hz, 200μs), (800Hz, 175μs) and (800Hz, 105μs); or

[0095] (vii) (800Hz, 105μs), (800Hz, 175μs), (1000Hz, 150μs) and (1000Hz, 90μs).

[0096] The selected frequencies and pulse widths can be above or within one or more linearly defined regions defined by the following points:

[0097] (i) (1 kHz, 98.3μs), (1 kHz, 109μs), (4 kHz, 71.4μs) and (4 kHz, 64.6μs); or (ii) (4 kHz, 71.4μs), (4 kHz, 64.6μs), (7 kHz, 44.2μs) and (7 kHz, 48.8μs); or

[0098] (iii) (7 kHz, 44.2μs), (7 kHz, 48.8μs), (10 kHz, 29.9μs) and (10 kHz, 27.1μs).

[0099] or

[0100] (i) (1 kHz, 96.3μs), (1 kHz, 112μs), (4 kHz, 73.8μs) and (4 kHz, 62.2μs); or (ii) (4 kHz, 73.8μs), (4 kHz, 62.2μs), (7 kHz, 43.6μs) and (7 kHz, 49.4μs); or

[0101] (iii) (7 kHz, 43.6 μβ), (7 kHz, 49.4 μβ), (10 kHz, 30.0 μβ), and (10 kHz, 27.0 μβ).

[0102] (i) (1 kHz, 50.0 μβ), (1 kHz, 200.0 μβ), (4 kHz, 110.0 μβ), and (4 kHz, 30.0 μβ); or

[0103] (ii) (4 kHz, 110.0 μβ), (4 kHz, 30.0 μβ), (7 kHz, 30.0 μβ), and (7 kHz, 60.0 μβ); or

[0104] (iii) (7 kHz, 30.0 μβ), (7 kHz, 60.0 μβ), (10 kHz, 40.0 μβ), and (10 kHz, 20.0 μβ).

[0105] (i) (1 kHz, 50.0 μβ), (1 kHz, 200.0 μβ), (4 kHz, 110.0 μβ), and (4 kHz, 30.0 μβ); or

[0106] (ii) (4 kHz, 110.0 μβ), (4 kHz, 30.0 μβ), (7 kHz, 30.0 μβ), and (7 kHz, 60.0 μβ); or

[0107] (iii) (7 kHz, 30.0 μβ), (7 kHz, 60.0 μβ), (10 kHz, 40.0 μβ), and (10 kHz, 20.0 μβ).

[0108] Frequency and pulse width can be selected based on information relating to the frequency and pulse width at which the therapy pulses are formed to cause the sub-perception stimulation to occur at the therapy location. The first and second sets of stimulation parameters can be provided to the spinal cord stimulator by an external device, and wherein the information is stored on the external device. The information can be stored in the spinal cord stimulator. The frequency and pulse width can be selected using the information to be the frequency and pulse width that requires the lowest amount of power for the therapy pulses.

[0109] The method can further include steering the current between the plurality of electrodes to adjust the therapy location to a new therapy location relative to the array. The method can further include adjusting the amplitude of the therapy pulses based on the new therapy location.

[0110] The method can further include steering the current between the plurality of electrodes to adjust the therapy location to a new therapy location relative to the array. The method can further include adjusting the amplitude of the therapy pulses based on the new therapy location.

[0111] The method can further include steering the current between the plurality of electrodes to adjust the therapy location to a new therapy location relative to the array. The method can further include adjusting the amplitude of the therapy pulses based on the new therapy location.

[0112] The determined first set of stimulation parameters can include a first amplitude of the test pulse, and the method can further include, in response to the instruction, deriving a second set of stimulation parameters from the determined first set of stimulation parameters by reducing the first amplitude to a second amplitude for the therapy pulse. The first amplitude can be reduced to the second amplitude by a certain amount or percentage or by a certain amount or percentage.

[0113] The method can further include adjusting at least one of the stimulation parameters in the second set of stimulation parameters in response to a change in the patient's position or activity. The spinal cord stimulator can be programmed during a programming session, and the therapy pulse can be ramped in over a period of one hour or less during the programming session to cause sub-perception stimulation to occur at the therapy location.

[0114] In a fourth example, a system for programming a spinal cord stimulator having a plurality of electrodes including an array can include an external system, a non-transitory computer readable medium containing instructions that, when executed, allow for providing a plurality of different sets of stimulation parameters to the spinal cord stimulator, where each first set of stimulation parameters causes the spinal cord stimulator to form a biphasic test pulse at at least two of the electrodes, where each biphasic test pulse includes a first phase having a first polarity and a second phase having a second polarity opposite the first polarity, where the first pulse phase and the second pulse phase are both actively driven by stimulation circuitry in the spinal cord stimulator, and where each first set of stimulation parameters causes suprathreshold stimulation to occur at different locations relative to the array; where, after determining a set of first stimulation parameters that treats a pain symptom of a patient, the determined first set of stimulation parameters corresponds to a therapy location relative to the array, the instructions, when executed, further allow for the external device to provide a second set of stimulation parameters to the spinal cord stimulator to cause the spinal cord stimulator to form a therapy pulse at at least two of the electrodes, where the second set of stimulation parameters causes sub-perception stimulation to occur at the therapy location.

[0115] The biphasic test pulse is formed at 130 Hz or less. The charge of the first phase can be equal to the charge of the second phase. The duration of the first phase can be different than the duration of the second phase, and the amplitude of the first phase can be different than the amplitude of the second phase. The biphasic test pulse can include a symmetric biphasic pulse, where the duration of the first phase is equal to the duration of the second phase, and where the amplitude of the first phase is equal to the amplitude of the second phase but has a polarity opposite the amplitude of the second phase. The charge of the first phase can not be equal to the charge of the second phase.

[0116] The treatment pulses can include biphasic pulses having a first phase having a first polarity and a second phase having a second polarity opposite the first polarity. The treatment pulses can include symmetric biphasic pulses, where a duration of the first phase is equal to a duration of the second phase, and where an amplitude of the first phase is equal to an amplitude of the second phase but has an opposite polarity to the amplitude of the second phase.

[0117] The non-transitory computer-readable instructions can be configured to determine the second set of stimulation parameters by adjusting at least one of the stimulation parameters of the determined first set of stimulation parameters without adjusting the treatment location relative to the array. The determined first set of stimulation parameters can include a set of stimulation parameters for which a patient responds favorably to treatment of a pain symptom.

[0118] Each of the first set of stimulation parameters can cause the suprathreshold stimulation to occur as a multipole at the different locations. At least some or all of the first set of stimulation parameters can cause the suprathreshold to occur as a bipolar at the different locations. At least some of the first set of stimulation parameters can cause the suprathreshold to occur as a virtual bipolar at the different locations. The second stimulation parameter can cause the subthreshold stimulation to occur as a multipole at the treatment location. The second stimulation parameter can cause the subthreshold stimulation to occur as a bipolar at the treatment location. The second stimulation parameter can cause the subthreshold stimulation to occur as a virtual bipolar at the treatment location.

[0119] The determined first set of stimulation parameters can be determined using feedback from the patient. The determined first set of stimulation parameters can include an amplitude of a test pulse, and wherein the second set of stimulation parameters includes an amplitude of a treatment pulse, and wherein the amplitude of the treatment pulse is lower than the amplitude of the test pulse. The determined first set of stimulation parameters can differ from the second set of stimulation parameters in only the amplitude of the test pulse and the treatment pulse.

[0120] Each of the first set of stimulation parameters and the second set of stimulation parameters can include an indication of which of at least two electrodes is active, an indication of a polarity of the at least two electrodes, and an indication of an amplitude of a current at the at least two electrodes.

[0121] The second set of stimulation parameters can include a frequency and a pulse width of the treatment pulse, wherein the frequency is 10 kHz or lower, and at least one of the frequency and the pulse width is selected by the computer-readable medium to cause the subthreshold stimulation to occur. The selected frequency and pulse width can be above or within one or more linearly defined regions defined by the following points:

[0122] (i) (10 Hz, 265 μs), (10 Hz, 435 μs), (50 Hz, 370 μs) and (50 Hz, 230 μs); or (ii) (50 Hz, 230 μs), (50 Hz, 370 μs), (100 Hz, 325 μs) and (100 Hz, 195 μs); or

[0123] (iii) (100 Hz, 195 μs), (100 Hz, 325 μs), (200 Hz, 260 μs) and (200 Hz, 160 μs); or

[0124] (iv) (200 Hz, 160 μs), (200 Hz, 260 μs), (400 Hz, 225 μs) and (400 Hz, 140 μs); or

[0125] (v) (400 Hz, 140 μs), (400 Hz, 225 μs), (600 Hz, 200 μs) and (600 Hz, 120 μs); or

[0126] (vi) (600 Hz, 120 μs), (600 Hz, 200 μs), (800 Hz, 175 μs) and (800 Hz, 105 μs); or

[0127] (vii) (800 Hz, 105 μs), (800 Hz, 175 μs), (1000 Hz, 150 μs) and (1000 Hz, 90 μs).

[0128] The selected frequencies and pulse widths can be above or within one or more linearly defined regions defined by the following points:

[0129] (i) (1 kHz, 98.3 μs), (1 kHz, 109 μs), (4 kHz, 71.4 μs) and (4 kHz, 64.6 μs); or (ii) (4 kHz, 71.4 μs), (4 kHz, 64.6 μs), (7 kHz, 44.2 μs) and (7 kHz, 48.8 μs); or

[0130] (iii) (7 kHz, 44.2 μs), (7 kHz, 48.8 μs), (10 kHz, 29.9 μs) and (10 kHz, 27.1 μs).

[0131] or

[0132] (i) (1kHz, 96.3μs), (1kHz, 112μs), (4kHz, 73.8μs), and (4kHz, 62.2μs); or (ii) (4kHz, 73.8μs), (4kHz, 62.2μs), (7kHz, 43.6μs), and (7kHz, 49.4μs); or

[0133] (iii) (7kHz, 43.6μs), (7kHz, 49.4μs), (10kHz, 30.0μs) and (10kHz, 27.0μs).

[0134] or

[0135] (i) (1kHz, 69.6μs), (1kHz, 138.4μs), (4kHz, 93.9μs), and (4kHz, 42.1μs); or

[0136] (ii) (4kHz, 93.9μs), (4kHz, 42.1μs), (7kHz, 33.4μs) and (7kHz, 59.6μs); or

[0137] (iii) (7kHz, 33.4μs), (7kHz, 59.6μs), (10kHz, 35.2μs) and (10kHz, 21.8μs).

[0138] or

[0139] (i) (1kHz, 50.0μs), (1kHz, 200.0μs), (4kHz, 110.0μs) and (4kHz, 30.0μs); or

[0140] (ii) (4kHz, 110.0μs), (4kHz, 30.0μs), (7kHz, 30.0μs) and (7kHz, 60.0μs); or

[0141] (iii) (7kHz, 30.0μs), (7kHz, 60.0μs), (10kHz, 40.0μs) and (10kHz, 20.0μs).

[0142] The frequency and pulse width can be selected by a computer-readable medium based on information relating to the frequency and pulse width at which a therapeutic pulse is formed to cause subsensory stimulation at the therapeutic location. This information can be used to select the frequency and pulse width as the minimum power required for the therapeutic pulse.

[0143] The computer-readable medium can include instructions that, when executed, allow the external device to direct the current between the plurality of electrodes to adjust the therapy location to a new therapy location relative to the array. The computer-readable medium can also include instructions that, when executed, allow the external device to adjust the amplitude of the therapy pulses based on the new therapy location. The computer-readable medium can also include instructions that, when executed, allow the external device to decrease at least one of the stimulation parameters in the second set of stimulation parameters by an amount or percentage or by an amount or percentage.

[0144] The computer-readable medium can also include instructions that, when executed, allow the external device to adjust at least one of the stimulation parameters in the second set of stimulation parameters in response to a change in the patient's position or activity. The computer-readable medium can also include instructions that, when executed, allow the external device to program the spinal cord stimulator during a programming session, and wherein the instructions are configured to wash in the therapy pulses for an hour or less during the programming session to cause sub-threshold stimulation to occur at the therapy location. BRIEF DESCRIPTION OF DRAWINGS

[0145] Figure 1 An implantable pulse generator (IPG) usable for spinal cord stimulation (SCS) is shown in accordance with the prior art.

[0146] Figure 2 An example of a stimulation pulse that can be generated by the IPG is shown in accordance with the prior art.

[0147] Figure 3 Use of an external trial stimulator (ETS) to provide stimulation prior to IPG implantation is shown in accordance with the prior art.

[0148] Figure 4 Various external devices capable of communicating with and programming stimulation in the IPG and ETS are shown in accordance with the prior art.

[0149] Figure 5 A graphical user interface (GUI) of a clinician programmer external device for setting or adjusting stimulation parameters is shown in accordance with the prior art.

[0150] Figure 6 A sweetspot search for determining effective electrodes for a patient using a moveable sub-perception bipolar is shown.

[0151] Figures 7A-7D A sweetspot search for determining effective electrodes for a patient using a moveable super-perception bipolar is shown.

[0152] Figure 8Stimulation circuitry that can be used in an IPG or ETS is shown that is capable of providing multiple independent current controls for independently setting the current at each of the electrodes.

[0153] Figure 9 A flowchart of a study performed on various patients with back pain is shown that was designed to determine optimal sub-perception SCS stimulation parameters in the frequency range of 1 kHz to 10 kHz.

[0154] Figures 10A-10C Various study results are shown as a function of stimulation frequency in the 1 kHz to 10 kHz frequency range, including: average optimal pulse width ( Figure 10A ), average charge per second and optimal stimulation amplitude ( Figure 10B ), and back pain score ( Figure 10C ).

[0155] Figures 11A-11C An analysis of the relationship between average optimal pulse width and frequency in the 1 kHz to 10 kHz frequency range is also shown, as well as regions that are statistically-significant in identifying optimization of these parameters.

[0156] Figure 12A Results of patients tested with sub-perception therapy at 1 kHz frequency or below are shown, and the optimal pulse width range determined at the tested frequency, as well as the region of optimal pulse width v. frequency for sub-perception therapy is shown.

[0157] Figure 12B Various modeled relationships between average optimal pulse width and frequency at or below 1 kHz are shown.

[0158] Figure 12C A study of the duty cycle of optimal pulse width as a function of frequency at or below 1 kHz is shown.

[0159] Figure 12D Average battery current and battery discharge time at optimal pulse width as a function of frequency at or below 1 kHz is shown.

[0160] Figure 13 A fitting module is shown that shows how the relationships and regions determined regarding optimal pulse width and frequency (≤ 10 kHz) can be used to set sub-perception stimulation parameters for an IPG or ETS.

[0161] Figure 14 An algorithm used for suprathreshold sweet spot searching prior to sub-perception therapy is shown, as well as possible optimization of sub-perception therapy using the fitting module.

[0162] Figure 15 An alternative algorithm for optimizing sub-perception therapy using a fitting module is shown. DETAILED DESCRIPTION

[0163] While spinal cord stimulation (SCS) therapy can be an effective means of alleviating pain in a patient, such stimulation can also result in paresthesia. Paresthesia (sometimes referred to as“supra-perception” therapy) is a sensation that can accompany SCS therapy, such as tingling, pricking, heat, cold, etc. Typically, the effects of paresthesia are mild, or at least do not unduly involve the patient. Moreover, paresthesia is generally a modest trade-off for patients for whom chronic pain has been controlled by SCS therapy. Some patients even find paresthesia to be comfortable and reassuring.

[0164] Nonetheless, for at least some patients, SCS therapy would ideally provide complete pain relief without paresthesia—often referred to as“sub-perception” or sub-threshold therapy that the patient does not feel. Effective sub-perception therapy can provide pain relief without paresthesia by emitting stimulation pulses at higher frequencies. Unfortunately, such higher frequency stimulation can require more power, which tends to deplete the battery 14 of the IPG 10. See, e.g., U.S. Patent Application Publication 2016 / 0367822. If the battery 14 of the IPG is a primary battery and not rechargeable, then high frequency stimulation means that the IPG 10 will need to be replaced more quickly. Alternatively, if the IPG battery 14 is rechargeable, then the IPG 10 will need to be charged more frequently over longer periods of time. Either way, this can be inconvenient for the patient.

[0165] In SCS applications, it is desirable to determine a stimulation program that will be effective for each patient. An important part of determining an effective stimulation program is determining the“sweet spot” for stimulation in each patient, i.e., selecting which electrodes should be active (E) and with what polarity (P) and relative amplitude (X%) to recruit and thus treat the nerve site where the source of pain in the patient originates. Selecting electrodes that are proximate to this nerve site of the pain can be difficult to determine, and often trials are conducted to select the best combination of electrodes to provide therapy for the patient.

[0166] As described in U.S. Provisional Patent Application Serial No. 62 / 680,539, filed June 4, 2018, when using subsensory stimulation, selecting electrodes for a given patient can be even more difficult because the patient does not feel the stimulation, and therefore may have difficulty sensing whether the stimulation is “covering” his pain and thus whether the selected electrode is effective. Furthermore, subsensory stimulation may require a “wash-in” period before it can become effective. This wash-in period can take a day or more, and therefore subsensory stimulation may not be immediately effective, making electrode selection even more challenging.

[0167] Figure 6 The technique of the '539 application for dessert search is briefly described, namely, how electrodes can be selected for painful nerve sites 298 in a nearby patient when using subsensory stimulation. Figure 6 The technology is particularly useful in trial settings after patients have had an electrode array implanted for the first time (i.e., after receiving their IPG or ETS).

[0168] In the example shown, it is assumed that the pain site 298 is likely within tissue region 299. Such region 299 can then be deduced by a clinician based on the patient's symptoms (e.g., by understanding which electrodes are adjacent to specific vertebrae (not shown), such as within the T9-T10 intervertebral space). In the example shown, region 299 is defined by electrodes E2, E7, E15, and E10, meaning that electrodes outside this region (e.g., E1, E8, E9, E16) are unlikely to affect the patient's symptoms. Therefore, these electrodes may not be necessary. Figure 6 The desserts selected during the search are as described below.

[0169] exist Figure 6 In this design, a subsensory bipolar electrode 297a is selected, in which one electrode (e.g., E2) is chosen as the anode to generate a positive current (+A) to the patient's tissue, while the other electrode (e.g., E3) is chosen as the cathode to absorb a negative current (-A) from the tissue. This is similar to previous designs. Figure 2The description explains that biphasic stimulation pulses can be used with effective charge recovery. Because bipolar 297a provides subsensory stimulation, the amplitude A used during dessert search is down-titrated until the patient no longer experiences paresthesia. This subsensory bipolar 297a is provided to the patient over a period of time (such as several days), which allows the potential effectiveness of the subsensory bipolar to be "washed in" and allows the patient to provide feedback on how well the bipolar 297a helps the patient's symptoms. Such patient feedback can include pain scale rankings. For example, patients can use the Numerical Rating Scale (NRS) or the Visual Analogue Scale (VAS) to rank their pain on a scale from 1 to 10, where 1 represents no pain or almost no pain, and 10 represents the most imaginable pain. As discussed in the '539 application, such pain scale rankings can be input into the patient's external controller 45.

[0170] After testing the bipolar electrode 297a at this initial location, different combinations of electrodes (anode E3, cathode E4) are selected, which will move the bipolar electrode 297a to different positions within the patient's tissue. Again, the amplitude of the current A may need to be titrated to an appropriate sub-sensory level. In the example shown, the bipolar electrode 297a is moved downwards along one electrode lead and upwards along the other electrode lead, as shown in combination path 296 of the electrodes intended to cover the painful area 298. Figure 6 In the example, given a pain site 298 adjacent to electrodes E13 and E14, it can be expected that bipolar 297 at those electrodes will provide the best relief for the patient, as reflected in the patient's pain score ranking. Specific stimulation parameters selected when forming bipolar 297a can be selected at the GUI 64 of the clinician programmer 50 or other external device (such as the patient external controller 45) and wirelessly transmitted to the patient's IPG or ETS via a telemetry transmitter for execution.

[0171] Although Figure 6 The dessert search can be effective, but it can also be quite time-consuming when using subsensory stimuli. As already noted, subsensory stimuli were provided for several days at each bipolar 297 location, and because of the large number of bipolar locations selected, the entire dessert search could take up to a month to complete.

[0172] The inventors have determined via testing of SCS patients that it is beneficial to use suprathreshold stimulation during a sweet spot search to select active electrodes for a patient, even though it is expected that after the sweet spot search the patient will ultimately continue to be treated with subthreshold therapy. Using suprathreshold stimulation during a sweet spot search greatly accelerates the determination of active electrodes for a patient compared to using subthreshold stimulation, which requires a wash-in period at each set of electrodes being tested. After using suprathreshold therapy to determine electrodes for a patient, the therapy can be titrated to a subthreshold level that maintains the same electrodes determined for the patient during the sweet spot search. Since the selected electrodes are known to be recruiting the neural sites of the patient's pain, applying subthreshold therapy to those electrodes is more likely to have an immediate effect, thereby reducing or potentially eliminating the need to wash-in the subsequent subthreshold therapy. In summary, when a suprathreshold sweet spot search is utilized, effective subthreshold therapy can be achieved more quickly for a patient. Preferably, the suprathreshold sweet spot search occurs using symmetric biphasic pulses such as occur at low frequencies between 40 Hz and 200 Hz in one example.

[0173] According to one aspect of the disclosed technology, a patient will be provided subthreshold therapy. A sweet spot search to determine electrodes that can be used during subthreshold therapy can precede such subthreshold therapy. In some aspects, when subthreshold therapy is used for a patient, the sweet spot search can use as subthreshold the bipolar 297a Figure 6 ), as just described. This can be relevant because the subthreshold sweet spot search can match the final subthreshold therapy that the patient will receive.

[0174] However, the inventors have determined that even though a subthreshold therapy will ultimately be used for a patient, it can be beneficial to use suprathreshold stimulation (i.e., stimulation with attendant paresthesia) during a sweet spot search. This is shown in Figure 7A , where the movable bipolar 301a provides suprathreshold stimulation that can be felt by the patient. In contrast to the subthreshold bipolar 297a in Figure 6 , providing bipolar 301a as suprathreshold stimulation can simply involve increasing its amplitude (e.g., current A), although other stimulation parameters can also be adjustable such as by providing a longer pulse width.

[0175] The inventors have determined that it is beneficial to take suprathreshold stimulation during a sweet spot search even though a subthreshold therapy will ultimately be used for a patient.

[0176] First, as noted above, using super-perception therapy by definition allows the patient to feel the stimulation, which enables the patient to provide feedback to the clinician essentially immediately as to whether the sensation seems to cover the pain site 298 well. In other words, there is no need to spend time ramping in the bipolar 301a at each location as it is moved along the path 296. Thus, the appropriate bipolar 301a proximate to the patient's pain site 298 can be established much more quickly, such as within a single clinician's office visit, rather than over the course of days or weeks. In one example, when searching for a super-perception sweet spot prior to sub-perception therapy, the time required to ramp in the sub-perception therapy can be 1 hour or less, 10 minutes or less, or even on the order of a few seconds. This allows ramping in to occur during a single programming session for the patient's IPG or ETS, and does not require the patient to leave the clinician's office.

[0177] Second, using super-perception stimulation during the sweet spot search ensures that the electrodes are determined that recruit the pain site 298 well. As a result, after the sweet spot search is complete and the final sub-perception therapy is titrated for the patient, ramping in of that sub-perception therapy can be performed for a much shorter time, as the electrodes needed for good recruitment are already confidently determined.

[0178] Figures 7B-7D Other super-perception bipolars 301b-301d that can be used are shown, and in particular how a virtual bipolar can be formed using three or more of the electrodes 16 by activating them. Virtual poles are further discussed in U.S. Provisional Patent Application Serial No. 62 / 598,114, filed December 13, 2017, and thus are only briefly described here. Virtual poles are formed with the assistance of the stimulation circuit 28 or 44 used in the IPG or ETS if it is capable of setting the current independently at any of the electrodes - this is sometimes referred to as multiple independent current control (MICC), discussed below with respect to Figure 8 Further explanation of this is provided.

[0179] When using virtual bipolars, the GUI 64( Figure 4 ) in the clinician programmer 50( Figure 5 ) can be used to define the anode pole (+) and the cathode pole (-) at locations 291( Figure 7B ) that can not necessarily correspond to the locations of the physical electrodes 16. The control circuit 70 in the clinician programmer 50 can calculate from these locations 291 and from other tissue modeling information which physical electrodes 16 will need to be selected and at what amplitudes to form the virtual anode and virtual cathode at the specified locations 291. As previously described, the amplitudes at the selected electrodes can be expressed as a percentage X% of the total current amplitude A specified at the GUI 64 of the clinician programmer 50.

[0180] For example, in Figure 7B the virtual anode pole is positioned at a location 291 between electrodes E2, E3 and E10. The clinician programmer 50 can then calculate, based on this location, the appropriate share (X% ) of the total anode current +A that each of these electrodes will receive (during the first pulse phase 30a) to position the virtual anode at this location. Because the virtual anode is positioned closest to electrode E2, this electrode E2 can receive the largest share of the specified anode current +A (e.g., 75% *+A). Electrodes E3 and E10, which are adjacent to the virtual anode pole location but further away, receive a smaller share of the anode current (e.g., 15% *+A and 10% *+A, respectively). Likewise, it can be seen that, according to the specified location 291 of the virtual cathode pole adjacent to electrodes E4, E11 and E12, these electrodes will receive an appropriate share of the specified cathode current -A (e.g., 20% *-A, 20% *-A and 60% *-A, respectively, again during the first pulse phase 30a). These polarities will then be reversed during the second phase 30b of the pulse, as shown in the waveform in Figure 7B Regardless, the use of virtual poles in the formation of the bipolar 301b allows for shaping of the field in the tissue, and many different combinations of electrodes can be tried during the sweet spot search. In this regard, it is not strictly necessary to move the (virtual) bipolar sequentially along the path 296 for each electrode, and the path can be random, perhaps guided by feedback from the patient.

[0181] Figure 7C A useful virtual bipolar 301c configuration that can be used during the sweet spot search is shown. This virtual bipolar 301c again defines a target anode and cathode, whose locations do not correspond to the locations of physical electrodes. The virtual bipolar 301c is formed along a lead (essentially spanning the length of four electrodes from El to E5). This creates a larger field in the tissue that better recruits the pain site 298 of the patient. When moving along the path 296, this bipolar configuration 301c can need to be moved to fewer locations than the smaller bipolar configuration 301a in Figure 7A Figure 7D Extending on the bipolar configuration of Figure 7C to use electrodes formed on two leads to create a virtual bipolar 301d, e.g., from electrodes El to E5 and from electrodes E9 to E13. This bipolar 301d configuration needs to be moved along only a single path 296 parallel to these leads, as its field is large enough to recruit neural tissue adjacent to both leads. This can further speed up the pain site detection.

[0182] ​In some aspects, the super-ceptive dipole 301a-d used during the dessert search comprises a symmetrical biphasic waveform with identically pulsed width PW and identically amplitude of the pulse phases 30a and 30b (with flipped polarity during each phase) actively driven (e.g., by the stimulation circuit 28 or 44) (e.g., A 30a = A 30b , and PW 30a = PW 30b ). This is beneficial because the second pulse phase 30b provides for an activation charge recovery, where in this case the charge (Q 30a ) provided during the first pulse phase 30a is equal to the charge (Q 30b ) of the second pulse phase 30b, so that these pulses are charge balanced. The use of a biphasic waveform is also considered beneficial because, as known, cathodes are heavily involved in neural tissue recruitment. When using biphasic pulses, the position of the (virtual) anode and cathode will flip during the two phases of the pulse. This effectively doubles the neural tissue targeted for stimulation recruitment, and thus increases the likelihood that the pain site 298 will be covered by the dipole at the correct location.

[0183] The super-ceptive dipole 301a-b does not need to comprise a symmetrical biphasic pulse as just described, however. For example, the amplitudes and pulse widths of the two phases 30a and 30b can be different, while keeping the charges (Q) of the two phases balanced (e.g., Q 30a = A 30a * PW 30a = A 30b * PW 30b = Q 30b ). Alternatively, the two phases 30a and 30b can be charge unbalanced (e.g., Q 30a = A 30a * PW 30a > A 30b * PW 30b = Q 30b , or Q 30a = A 30a * PW 30a > A 30b * PW 30b = Q 30b ). In summary, the pulses in the dipole 301-301d can be biphasic symmetrical (and thus inherently charge balanced), biphasic non-symmetrical but still charge balanced, or biphasic non-symmetrical and charge unbalanced.

[0184] In a preferred example, the frequency F of the super-perception pulses 301a-d used during the super-perception sweet spot search can be 10 kHz or lower, 1 kHz or lower, 500 Hz or lower, 300 Hz or lower, 200 Hz or lower, 130 Hz or lower, or 100 Hz or lower, or a range bounded by two of these frequencies (e.g., 100 to 130 Hz, or 100 to 200 Hz). In a particular example, a frequency of 90 Hz, 40 Hz, or 10 Hz can be used, with the pulses comprising biphasic pulses that are preferably symmetrical. However, a single actively driven pulse phase followed by a passive recovery phase can also be used. The pulse width PW can also comprise a value in the range of hundreds of microseconds, such as 150 microseconds to 400 microseconds. Because the purpose of the super-perception sweet spot search is simply to determine the electrodes that properly cover the patient's pain, the frequency and pulse width can not be as important at this stage. Once the electrodes are selected for sub-perception stimulation, the frequency and pulse width can be optimized, as discussed further below.

[0185] It should be understood that the super-perception bipole 301a-d used during the sweet spot search need not be the same electrodes selected for subsequent sub-perception therapy to the patient. Rather, the optimal location of the bipole of interest during the search can be used as a basis for modifying the selected electrodes. Assume, for example, that the bipole 301a-d is used during the sweet spot search, and it is determined that the bipole provides the best pain relief when located at electrodes E13 and E14. At that point, the attempt at sub-perception therapy to the patient can continue using those electrodes E13 and E14. Alternatively, it can be prudent to modify the selected electrodes to see if the patient's symptoms can be further improved before attempting sub-perception therapy. For example, the distance (focal point) between the cathode and anode can be varied by using a virtual pole as already described. Or, a tri-pole (anode / cathode / anode) can be tried consisting of electrodes E12 / E13 / E14 or E13 / E14 / E15. See U.S. Provisional Patent Application Serial No. 62 / 598,114, filed December 13, 2017 (discussing tri-poles). Or electrodes on different leads can be tried in conjunction with E13 and E14. For example, because electrodes E5 and E6 are typically adjacent to electrodes E13 and E14, it can be useful to add E5 or E6 as a source of anodic or cathodic current (again creating a virtual pole). All of these types of adjustments should also be understood to include adjustments to the "location" of the applied therapy, even if the center point of the stimulation does not change (as can occur, for example, when varying the distance or focal point between the cathode and anode). Figure 7A

[0186] In one example with respect to Figure 8 A plurality of independent current controls (MICCs) are described in​Figure 8 The diagram shows a stimulation circuit 28 used in an IPG or ETS to generate a prescribed stimulus at the patient's tissue site. Figure 1 ) or 44 ( Figure 3 The stimulation circuits 28 or 44 can independently control the current or charge at each electrode, and use GUI 64 ( Figure 5 This allows current or charge to be directed to different electrodes, which is useful, for example, when moving bipolar 301i along path 296 during a dessert search. Figures 7A-7D The stimulation circuit 28 or 44 includes one or more current sources 440. i and one or more current sinks 442 i Source 440 i Hehui 442 i This can include digital-to-analog converters (DACs), and can be referred to as PDAC 440i and NDAC 442i based on the positive (generated, anode) current and negative (absorbed, cathode) current they emit, respectively. In the example shown, a pair of NDAC 440i... i / PDAC 442 i Dedicated (hardwired to) a specific circuit node ei 39. Each electrode node ei 39 is preferably connected to electrode Ei 16 via a DC blocking capacitor Ci 38, which acts as a safety measure to prevent DC current injection into the patient in the event of a possible circuit failure, for example, in stimulation circuits 28 or 44. PDAC 440 i and DNAC 442 i It may also include a voltage source.

[0187] Appropriate control of the PDACs 440i and NDACs 442i via the GUI 64 allows any of the electrodes 16 and the housing electrode Ec 12 to function as an anode or a cathode to generate current through the patient's tissue. Such control preferably occurs in the form of digital signals Iip and Iin that set the anode and cathode currents at each electrode Ei. If, for example, it is desired to set electrode E1 as an anode with a current of +3 mA, and to set electrodes E2 and E3 as cathodes each with a current of -1.5 mA, then the control signal I1p would be set to have a 3 mA digital equivalent to cause the PDAC 4401 to generate +3 mA, and the control signals I2n and I3n would be set to have a 1.5 mA digital equivalent to cause the NDACs 4422 and 4423 to each generate -1.5 mA. Note that the definition of these control signals can also occur using programmed amplitudes A and percentages X% set in the GUI 64. For example, A can be set to 3 mA, with E1 represented as an anode with X = 100%, and with E2 and E3 represented as cathodes with X = 50%. Alternatively, the control signals can not be set in percentages, and instead the GUI 64 can simply dictate that a current will occur at each electrode at any point in time.

[0188] In summary, the GUI 64 can be used to independently set the current at each electrode, or to direct the current between different electrodes. This is particularly useful in forming virtual bi-polars, which were previously explained to include activating more than two electrodes. The MICC also allows for more refined electric fields to be formed in the patient's tissue.

[0189] Other stimulation circuits 28 can also be used to implement the MICC. In an example not shown, a switch matrix can be interposed between one or more of the PDACs 440 i between the electrode nodes ei 39, and one or more of the NDACs 442 i between the electrode nodes. The switch matrix allows one or more of the PDACs and one or more of the NDACs to be connected to one or more of the electrode nodes at a given time. Various examples of stimulation circuits can be found in USP 6,181,969, 8,606,362, 8,620,436; US Patent Application Publications 2018 / 0071513, 2018 / 0071520; and US Provisional Patent Application Serial No. 62 / 559,247, filed September 15, 2017.

[0190] Many of the stimulation circuits 28 or 44, including the PDACs 440 i and the NDACs 442 iThe switch matrix (if present), and the electrode nodes ei 39) can be integrated on one or more application specific integrated circuits (ASICs), as described in U.S. Patent Application Publications 2012 / 0095529, 2012 / 0092031, and 2012 / 0095519. As explained in these documents, the one or more ASICs can also contain other circuitry that can be used in the IPG 10, such as telemetry circuitry (for interfacing with the telemetry antenna of the off-chip to the IPG or ETS), circuitry for generating a constant current output voltage (compliance voltage) VH to power the stimulation circuitry, various measurement circuitry, etc.

[0191] While it is preferred to use a sweet spot search (and in particular a super- perceptual sweet spot search) to determine the electrodes that will be used during subsequent sub- perceptual therapy, it should be noted that this is not strictly necessary. The sub- perceptual therapy can be guided by a sub-perceptual sweet spot search, or can be guided entirely without a sweet spot search. In any event, the sub-perceptual therapy as described next does not rely on the use of any sweet spot search.

[0192] In another aspect of the invention, the inventors have determined via testing of SCS patients that there is a statistically significant correlation between the pulse width (PW) and frequency (F) at which an SCS patient will experience a reduction in back pain without paresthesia (sub-perceptual). Using this information can help determine what pulse width is likely to be optimal for a given SCS patient based on a particular frequency, and what frequency is likely to be optimal for a given SCS patient based on a particular pulse width. Advantageously, this information suggests that sub-perceptual SCS stimulation without paresthesia can occur at frequencies of 10 kHz and below 10 kHz. The use of such low frequencies allows the use of sub-perceptual therapy with much lower power consumption in the patient's IPG or ETS.

[0193] Figures 9-11C Results derived from testing patients at frequencies ranging from 1 kHz to 10 kHz are shown. Figure 9 How the data was collected from actual SCS patients, and the criteria for inclusion of patients in the study are explained. Patients with back pain but not receiving SCS therapy were first identified. Key patient inclusion criteria were: persistent lower back pain for more than 90 days; NRS pain scale of 5 or greater (NRS is explained below); stable opioid therapy for 30 days; and baseline functional disability index score greater than or equal to 20 and less than or equal to 80. Key patient exclusion criteria were: back surgery within the previous 6 months; presence of other confounding medical / psychological conditions; and untreated major psychiatric illness or serious drug-related performance problems.

[0194] After such initial screening, the patients periodically enter their qualitative indicators of pain (i.e., pain scores) into a portable electronic diary device, which can include the patient external controller 45, and the external controller 45 can in turn transmit its data to the clinician programmer 50 Figure 4 ). Such pain scores can include a numerical rating scale (NRS) score from 1 to 10, and can be entered into the electronic diary three times per day. As shown in Figure 10C , the baseline NRS scores for patients who ultimately were not excluded from the study and who also did not receive sub-perception stimulation therapy were approximately 6.75 / 10, with a standard error SE (sigma / SQRT(n)) of 0.25.

[0195] Returning to Figure 9 , the patients then have the lead 15' ( Figure 3 ) implanted on the left and right sides of the spinal column, and are provided with external trial stimulation as previously described. The clinician programmer 50 is used to provide stimulation programs to the ETS 40 of each patient, as previously described. This is done to confirm that SCS therapy is helpful in alleviating their pain for a given patient. If SCS therapy is not helpful for a given patient, the trial lead 15' is removed, and the patient is then excluded from the study.

[0196] Those patients for whom the external trial stimulation is helpful ultimately receive full implantation of a permanent IPG 10, as previously described. After a healing period, and again using the clinician programmer 50, the "sweet spot" for stimulation is located in each patient, i.e., which electrodes should be active (E) and with what polarity (P) and relative amplitude (X%) to recruit and thus treat the neural site in the patient. The sweet spot search can occur in any manner previously described with respect to Figures 6-7D , but in the preferred embodiment will include super-perception stimulation (e.g., such as 7A-7D) due to the previously described benefits. However, this is not strictly necessary, and sub-perception stimulation can also be used during the sweet spot search. In the example of Figure 9 , the sweet spot search occurs at 10 kHz, but again the frequency used during the sweet spot search can vary. Symmetric biphasic pulses are used during the sweet spot search, but again this is not strictly necessary. A decision is made as to which electrodes should be active starting with the electrodes 16 present between the thoracic vertebrae T9 and T10. However, electrodes as far as T8 and T11 can also be activated if necessary. The fluoroscopic images of the lead 15 within each patient are used to determine which electrodes are proximate to the vertebrae T8, T9, T10, and T1.

[0197] During the sweet spot search, bipolar stimulation using only two electrodes was used for each patient, and only adjacent electrodes were used on a single lead 15, similar to that described in Figure 6 and Figure 7A . Thus, one patient's sweet spot can include stimulation of adjacent electrodes E4 (as cathode) and E5 (as anode) on the left lead 15, as previously shown in Figure 2 ( electrodes can be between T9 and T10), while another patient's sweet spot can include stimulation of adjacent electrodes E9 (as anode) and E10 (as cathode) on the right lead 15 (electrodes can be between T10 and T11). Bipolar stimulation using only adjacent electrodes and only between vertebrae T8 to T11 was desired to minimize variation in treatment and symptoms between patients in the study. However, more complex bipolars such as those described with respect to Figures 7B-7D may also be used during the sweet spot search. If a patient has sweet spot electrodes in the desired thoracic position, and if they experience 30% or greater pain relief per NRS score, such patients continue in the study; patients who do not meet these criteria are excluded from further study. While the study initially started with 39 patients, 19 patients were excluded from the study by Figure 9 , leaving a total of 20 patients remaining.

[0198] The remaining 20 patients then undergo a "washout" period, meaning that their IPG does not provide stimulation for a period of time. In particular, the patients' NRS pain scores are monitored until their pain reaches 80% of their initial baseline pain. This is to ensure that the benefits of the previous stimulation do not carry over to the next analysis period.

[0199] The remaining patients then undergo sub-perception SCS therapy using the previously determined sweet spot electrodes at different frequencies in the range of 1 kHz to 10 kHz. However, this is not strictly necessary, as the current at each electrode is also independently controlled to help shape the electric field in the tissue, as previously described. As shown in Figure 9 , each patient is tested using stimulation pulses having frequencies of 10 kHz, 7 kHz, 4 kHz, and 1 kHz. For simplicity, Figure 9 shows that these frequencies are tested sequentially for each patient, but in practice the frequencies are applied to each patient in a random order. Once testing at a given frequency is complete, a washout period precedes the start of testing at another frequency.

[0200] At each frequency being tested, the amplitude (A) and pulse width (PW) of the stimulation are adjusted and optimized for each patient (first pulse phase 30a; Figure 2), so that each patient experiences possible good pain relief without paresthesia (sub-perception). In particular, using the clinician programmer 50, and leaving the same sweet spot electrodes activated as previously determined (although again this is not strictly necessary), each patient is stimulated at a low amplitude (e.g., 0) that is increased to a maximum point at which paresthesia can be noticed by the patient (perception threshold). An initial stimulation is then selected for the patient at 50% of the maximum amplitude, i.e., such that the stimulation is sub-perception and thus without paresthesia. However, other percentages of the maximum amplitude (80%, 90%, etc.) can also be selected, and can vary with patient activity or position, as further explained below. In one example, the stimulation circuit 28 or 44 in the IPG or ETS can be configured to receive instructions from the GUI 64 via a selectable option (not shown) to reduce the amplitude of the stimulation pulses to or by an amount or percentage, such that the pulses can be made sub-perception if they are not already sub-perception. Other stimulation parameters (e.g., pulse width, charge) can also be reduced to the same effect.

[0201] The patient will then leave the clinician's office, and thereafter and in communication with the clinician (or his technician or programmer) will use his external controller 45 Figure 4 to make adjustments to his stimulation (amplitude and pulse width). At the same time, the patient will enter NRS pain scores in his electronic diary (e.g., external controller), again three times per day. Patient adjustments to amplitude and pulse width are typically an iterative process, but essentially try adjustments based on feedback from the patient to adjust the therapy to reduce their pain, while still ensuring that the stimulation is sub-perception. The testing at each frequency lasts approximately 3 weeks, and stimulation adjustments can be made every couple of days or so. At the end of the testing period at a given frequency, the best amplitude and pulse width have been determined for each patient and recorded for each patient along with the patient NRS pain scores for those best parameters entered in their electronic diary.

[0202] In one example, the percentage of the maximum amplitude used to provide sub-perception stimulation can be selected depending on the patient's activity level or position. In this regard, the IPG or ETS can include a means for determining patient activity or position, such as an accelerometer. If the accelerometer indicates a high level of patient activity or a position in which the electrodes will be further away from the spinal cord (e.g., lying down), the amplitude can be increased to a higher percentage to increase the current (e.g., 90% of the maximum amplitude). If the patient is experiencing a lower level of activity or a position in which the electrodes will be closer to the spinal cord (e.g., standing), the amplitude can be decreased (e.g., to 50% of the maximum amplitude). Although not shown, the GUI 64 Figure 5) can include setting a percentage of the maximum amplitude at which paresthesia becomes noticeable to the patient, thereby allowing the patient to adjust the sub-perception current amplitude.

[0203] Preferably, multiple independent current control (MICC) is used to provide or adjust the sub-perception therapy, as previously discussed with respect to Figure 8 This allows for independent setting of the current at each electrode to facilitate steering of current or charge between electrodes, helping to form a virtual bipolar, and more generally to shape the electric field in the patient's tissue. In particular, the MICC can be used to steer the sub-perception therapy to different locations in the electrode array and thus the spinal cord. For example, once a set of sub-perception stimulation parameters has been selected for a patient, one or more of the stimulation parameters can be changed. Such changes can be warranted or dictated by the therapy location. The patient's physiology can vary at different spinal locations, and the tissue can be more or less conductive at different therapy locations. Thus, if the sub-perception therapy location is steered to a new location along the spinal cord (which can include changing the anode / cathode distance or focal point), it can be warranted to adjust at least one of the stimulation parameters, such as the amplitude. As noted earlier, sub-perception adjustment is facilitated and can occur in a programming session, as a substantial wash-in period can not be necessary.

[0204] Adjustment of the sub-perception therapy can also include changing other stimulation parameters, such as pulse width, frequency, and even the interphase period (IP) duration Figure 2 ). The interphase duration can affect the neural dosage, or rate of charge infusion, such that a higher sub-perception amplitude would be used with a shorter interphase duration. In one example, the interphase duration can be varied between 0 and 3 ms. After a wash-out period, the same protocol can be used to test a new frequency, as described.

[0205] The sub-perception stimulation pulses used are symmetric biphasic constant current amplitude pulses, with a first pulse phase 30a and a second pulse phase 30b (of the same duration) (see Figure 2 ). However, constant voltage amplitude pulses can also be used. Pulses of different shapes (triangular, sinusoidal, etc.) can also be used. When providing sub-perception therapy, a pre-pulse (i.e., a small current provided before the actively driven pulse phase) can also occur to affect the polarization or depolarization of the neural tissue. See, e.g., USP 9,008,790.

[0206] Figures 10A-10C Results of testing patients at 10 kHz, 7 kHz, 4 Hz, and 1 kHz are shown. Data is shown in each graph as the average for 20 remaining patients at each frequency, with error bars reflecting the standard error (SE) between patients.

[0207] With Figure 10B Starting with the optimized amplitudes A shown for the 20 remaining patients at the frequencies being tested. Interestingly, the optimal amplitude at each frequency is essentially constant, at about 3 mA. Figure 10B The amount of energy consumed at each frequency is also shown, more particularly the mean charge per second (MCS) attributable to the pulses (in mC / s) is shown. The MCS value can include the neuro dose, calculated by taking the optimal pulse width (PW) (discussed below) and multiplying it by the optimal amplitude (A) and the frequency (F). The MCS is related to the current or power that must be consumed by the battery in the IPG 10 to form the optimal pulses. Notably, the MCS is significantly lower at lower frequencies: for example, the MCS at F = 1 kHz is approximately 1 / 3 of its value at higher frequencies (e.g., F = 7 kHz or 10 kHz). This means that optimal SCS therapy to relieve back pain without paresthesia can be achieved at lower frequencies like F = 1 kHz, with the added benefit of lower power draw to consider for the battery of the IPG 10 (or ETS 40). Figure 10A

[0208] Figure 10A The optimal pulse width is shown as a function of frequency in the 1 kHz to 10 kHz frequency range tested. As shown, this relationship follows a trend that is statistically significant: when modeled using a linear regression 98a, PW = -8.22F + 106, where pulse width is measured in microseconds and frequency in kilohertz, with a correlation coefficient R 2 = 0.974; when modeled using a polynomial regression 98b, PW = 0.486F 2 - 13.6F + 116, again where pulse width is measured in microseconds and frequency in kilohertz, with an even better correlation coefficient of R 2 = 0.998. Other fitting methods can be used to establish the following other information related to the frequency and pulse width at which stimulation pulses are to be formed to provide pain relief without paresthesia in the 1 kHz to 10 kHz frequency range.

[0209] Note that the relationship between optimal pulse width and frequency is not simply the expected relationship between frequency and duty cycle (DC) (i.e., the duration of time that the pulse is “on” divided by its period (1 / F)). In this regard, note that a given frequency has a natural effect on pulse width: it would be expected that higher frequency pulses would have a smaller pulse width. Thus, it would be expected that, for example, a 1 kHz waveform with a 100 microsecond pulse width would have the same clinical outcome as a 10 kHz waveform with a 10 microsecond frequency, since both waveforms have a 10% duty cycle. Figure 11A ​The duty cycle of the generation of the stimulation waveform using the optimal pulse width in the frequency range of 1 kHz to 10 kHz is shown. Here, the duty cycle is calculated by considering only the total 'on' time of the first pulse phase 30a Figure 2 ) ; the duration of the symmetric second pulse phase is ignored. This duty cycle is not constant in the 1 kHz to 10 kHz frequency range: for example, the optimal pulse width at 1 kHz (104 microseconds) is not simply 10 times the optimal pulse width at 10 kHz (28.5 microseconds). It is therefore important that the optimal pulse width is more than a mere scaling of the frequency.

[0210] Figure 10C The average patient pain scores at the optimal stimulation parameters (optimal amplitude Figure 7B ) and pulse width Figure 7A ) for each frequency in the range of 1 kHz to 10 kHz are shown. As noted earlier, the patients in this study initially reported a mean pain score of 6.75 prior to receiving SCS therapy. After SCS implantation and during the study, and with the amplitude and pulse width optimized during the interim sub-perception therapy, their average pain scores decreased significantly to an average pain score of about 3 for all frequencies measured.

[0211] Figure 11A An in-depth analysis of the generated relationship between optimal pulse width and frequency in the frequency range of 1 kHz to 10 kHz is provided. The graph in Figure 11A shows the average optimal pulse width for the 20 patients in the study at each frequency, along with the standard error generated from the variation between them. These are normalized at each frequency by dividing the standard error by the optimal pulse width, with the variation at each frequency ranging between 5.26% and 8.51%. From this, a variation of 5% (lower than all the values calculated) can be assumed as a variation with statistical significance at all frequencies measured.

[0212] According to this 5% variation, the maximum average pulse width (PW+5%) and the minimum average pulse width (PW-5%) can be calculated for each frequency. For example, the optimal average pulse width PW at 1 kHz is 104 microseconds, and 5% above this value (1.05*104μs) is 109 microseconds; 5% below this value (0.95*104) is 98.3 microseconds. Likewise, the optimal average pulse width AVG(PW) at 4 kHz is 68.0 microseconds, and 5% above this value (1.05*68.0μs) is 71.4 microseconds; 5% below this value (0.95*68.0μs) is 64.6 microseconds. Thus, a reduction in pain with statistical significance without paresthesia occurs within or above the linearly defined area 100a of points (1 kHz, 98.3μs), (1 kHz, 109μs), (4 kHz, 71.4μs), and (4 kHz, 64.6μs). A linearly defined area 100b around the points 102 is also defined for frequencies greater than or equal to 4 kHz and less than or equal to 7 kHz: (4 kHz, 71.4μs), (4 kHz, 64.6μs), (7 kHz, 44.2μs), (7 kHz, 48.8μs). A linearly defined area 100c around the points 102 is also defined for frequencies greater than or equal to 7 kHz and less than or equal to 10 kHz: (7 kHz, 44.2μs), (7 kHz, 48.8μs), (10 kHz, 29.9μs), (10 kHz, 27.1μs). Such areas 100 thus include information related to the frequencies and pulse widths at which stimulation pulses are to be formed to provide pain relief without paresthesia in the frequency range of 1 kHz to 10 kHz.

[0213] Figure 11B An alternative analysis of the resulting relationship between optimal pulse width and frequency is provided. In this example, the areas 100a to 100c are defined based on the calculated quasi-error (SE) at each frequency. Thus, the points 102 defining the corners of the areas 100a to 100c lie only within the range of the SE error bars at each frequency (PW+SE, and PW-SE), although these error bars have different sizes at each frequency. Thus, a reduction in pain with statistical significance without paresthesia occurs within or above the linearly defined area 100a of points (1 kHz, 96.3μs), (1 kHz, 112μs), (4 kHz, 73.8μs), and (4 kHz, 62.2μs). The linearly defined areas 100b and 100c are similar, and are not repeated here as they are set out in the graph at the top of Figure 11B of FIG. 1. The graph is set out in the graph at the top of FIG. 1.

[0214] Figure 11CAnother analysis of the resulting relationship between optimal pulse width and frequency is provided. In this example, regions 100a-c are defined based on the standard deviation (SD) calculated at each frequency, which is greater than the standard error (SE) measure used for that point. The points 102 defining the corners of regions 100a-c lie within the range of the SD error bars at each frequency (PW+SD, and PW-SD), although the points 102 can also be set within the error bars, similar to that described above. Figure 11A In any case, the reduction in pain with no paresthesia that is statistically significant occurs within or above the linearly defined region 100a of points (1 kHz, 69.6 μβ), (1 kHz, 138.4 μβ), (4 kHz, 93.9 μβ), and (4 kHz, 42.1 μβ). The linearly defined regions 100b and 100c are similar, and because the points 102 defining them are set at the top of the graph, they are not repeated here. Figure 11C

[0215] More generally, although not shown, the regions within the 1 kHz to 10 kHz frequency range that achieve a sub-perception therapeutic effect include the linearly defined region 100a (1 kHz, 50.0 μβ), (1 kHz, 200.0 μβ), (4 kHz, 110.0 μβ), and (4 kHz, 30.0 μβ); and / or the linearly defined region 100b (4 kHz, 110.0 μβ), (4 kHz, 30.0 μβ), (7 kHz, 30.0 μβ), and (7 kHz, 60.0 μβ); and / or the linearly defined region 100c (7 kHz, 30.0 μβ), (7 kHz, 60.0 μβ), (10 kHz, 40.0 μβ), and (10 kHz, 20.0 μβ).

[0216] In summary, one or more regions 100 with statistical significance can be defined for the following optimal pulse width and frequency data, taken for the patients in the study, to arrive at the combination of pulse width and frequency within the 1 kHz to 10 kHz frequency range that reduces pain without paresthetic side effects, and different statistical measures of error can be used to so define one or more regions.

[0217] Figures 12A-12D Results are shown for treating additional patients with sub-perception stimulation at frequencies at or below 1 kHz. The testing of patients generally occurs in a super-perception sweet spot search (see Figures 7A-7D ​After this occurs, although the subsensory electrodes used may vary depending on those used during the supersensory sweetness search (e.g., using MICC). Although the form of the pulses used during subsensory therapy may vary, symmetrical biphasic bipolar stimulation is still used to test patients for subsensory stimulation.

[0218] Figure 12A The relationship between the frequency and pulse width at which patients reported effective subsensory therapy for frequencies of 1 kHz and below 1 kHz is shown. Note the previous ( Figure 9 The same patient selection and testing criteria described can be used when evaluating frequencies at or below 1 kHz, where the frequency is adjusted as appropriate.

[0219] As can be seen, at each measured frequency, the optimal pulse width again falls within a certain range. For example, at 800 Hz, patients report good results when the pulse width falls within the range of 105 to 175 microseconds. The upper end of the pulse width range at each frequency is denoted as PW(High), and the lower end is denoted as PW(Low). PW(Medium) represents the middle (e.g., average) of PW(High) and PW(Low) at each frequency. At each measured frequency, the amplitude (A) of the current supplied is titrated down to a sub-sensory level so that the patient cannot perceive the sensory abnormality. Typically, the current is titrated to 80% of the threshold at which the sensory abnormality can be sensed. Because each patient's anatomy is unique, the sub-sensory amplitude A can vary from patient to patient. The pulse width data depicted includes the pulse width of only the first phase of the stimulation pulse.

[0220] Table 1 below presents the data in tabular form for frequencies of 1 kHz or below. Figure 12A The optimal pulse width and frequency data are provided, where the pulse width is expressed in microseconds:

[0221]

[0222]

[0223] Table 1

[0224] As previously described for frequencies in the range of 1kHz to 10kHz ( Figures 10A-11CThe data can be decomposed into distinct regions 300i, where effective subsensory therapy below 1 kHz is achieved. For example, regions of effective subsensory therapy can be linearly defined between various frequencies and high and low pulse widths that define effectiveness. For instance, at 10 Hz, PW(low) = 265 μs and PW(high) = 435 μs. At 50 Hz, PW(low) = 230 μs and PW(high) = 370 μs. Therefore, region 300a providing good subsensory therapy is defined by linearly defined regions at points (10 Hz, 265 μs), (10 Hz, 435 μs), (50 Hz, 370 μs), and (50 Hz, 230 μs). Table 2 defines the linearly constrained regions... Figure 12A Points in each of regions 300a to 300g shown in the figure:

[0225] Region Defined by points (Hz, μs) 300a (10,265),(10,435),(50,370),(50,230) 300b (50,230),(50,370),(100,325),(100,195) 300c (100,195),(100,325),(200,260),(200,160) 300d (200,160),(200,260),(400,225),(400,140) 300e (400,140),(400,225),(600,200),(600,120) 300f (600,120),(600,200),(800,175),(800,105) 300g (800,105),(800,175),(1000,150),(1000,90)

[0226] Table 2

[0227] The region of subsensory therapeutic effectiveness at frequencies of 1 kHz or below can be defined in other statistically significant ways, such as those previously described for frequencies in the 1 kHz to 10 kHz range. Figures 11A-11C For example, region 300i can be defined by referencing the pulse width PW(middle) at the midpoint of each range at each frequency. PW(middle) can include, for example, the average optimal pulse width reported by patients at each frequency, rather than a strict midpoint of the effective range reported by those patients. PW(high) and PW(low) can then be determined as the statistical variance of the average PW(middle) at each frequency and can be used to set the upper and lower boundaries of the effective subsensory region. For example, PW(high) can include the average PW(middle) plus a standard deviation or standard error, or a multiple of such a statistical measure; PW(low) can similarly include the average PW(middle) minus a standard deviation or standard error, or a multiple of such a statistical measure. PW(high) and PW(low) can also be determined from the average PW(middle) in other ways. For example, PW(high) can include the average PW(middle) plus a certain percentage, while PW(low) can include PW(middle) minus a certain percentage. In summary, one or more statistically significant regions 300 can be defined for optimal pulse width and frequency data at frequencies of 1 kHz or below 1 kHz to reduce pain without sensory abnormalities.

[0228] In addition Figure 12AShown in the middle is the average patient pain score (NRS score) reported by patients for different frequencies at 1 kHz or below using the optimal pulse width. Prior to receiving SCS therapy, patients initially reported an average pain score of 7.92. After SCS implantation, and using sub-perception stimulation at the optimal pulse width (with the range shown at each frequency), the average pain score of patients decreased significantly. At 1 kHz, 200 Hz, and 10 Hz, the average pain score reported by patients was 2.38, 2.17, and 3.20, respectively. Thus, clinical significance with respect to pain relief was demonstrated at 1 kHz or below using sub-perception therapy with the optimal width.

[0229] In Figure 12B the optimal pulse width versus frequency data in FIG. 3 was analyzed for frequencies at or below 1 kHz from the perspective of the mid-pulse width PW(mid) at each frequency (F). As shown, the relationships 310a through 310d followed a trend that was statistically significant, as evidenced by various regression models shown in FIG. 3 and summarized in Table 3 below: Figure 12A Figure 12B

[0230]

[0231] Table 3 Other fitting methods can be used to establish other information related to the frequencies and pulse widths at which stimulation pulses are formed to provide sub-perception pain relief without paresthesia.

[0232] Regression analysis can also be used to define regions of statistical relevance, such as 300a through 300g, where sub-perception therapy is effective at 1 kHz or below. For example, and although not shown in FIG. 3, a regression can be performed for PW(low) v. F to set the lower boundary of the region of relevance 300i, and a regression can be performed for PW(high) v. F to set the upper boundary of the region of relevance 300i.

[0233] Note that the relationship between optimal pulse width and frequency depicted in FIG. 3 is not simply the expected relationship between frequency and duty cycle (DC) as shown in FIG. 4. Figure 12B

[0234] Note that the relationship between optimal pulse width and frequency depicted in FIG. 3 is not simply the expected relationship between frequency and duty cycle (DC) as shown in FIG. 4. Figure 12A Figure 12C Figure 11A ​​​​Similarly, the duty cycle of the optimal pulse width is not constant at and below 1 kHz. Again, exceeding the optimal pulse width is only significant with respect to frequency scaling. Nevertheless, most pulse widths observed to be optimal at and below 1 kHz are greater than 100 microseconds. Such pulse widths are even impossible at higher frequencies. For example, at 10 kHz, the phases of two pulses must fit within a 100-microsecond time interval, making a pulse width (PW) longer than 100 microseconds even impossible.

[0235] Figure 12D Further benefits of using subsensory therapy at frequencies of 1 kHz and below are shown, namely reduced power consumption. Two sets of data were plotted. The first set of data includes the optimal pulse width for that patient using a battery in the patient's IPG or ETS. Figure 12A The average current drawn at each frequency (AVG Ibat) and the current amplitude A required to achieve subsensory stimulation for that patient (again, this amplitude can vary for each patient). At 1 kHz, the average battery current is approximately 1700 microamps. However, as the frequency decreases, the average battery current drops to approximately 200 microamps at 10 Hz. The second data set considers power consumption according to different advantages, namely the number of days an IPG or ETS with a fully charged rechargeable battery can operate before needing recharging (“discharge time”). Based on the average battery current data, it will be expected that when the average battery current is higher, the discharge time is lower at higher frequencies (e.g., approximately 3.9 days at 1 kHz, depending on various charging parameters and settings), and when the average battery current is lower, the discharge time is higher at lower frequencies (e.g., approximately 34 days at 10 Hz, depending on various charging parameters and settings). This is important: using the optimal pulse width not only provides effective subsensory therapy at frequencies of 1 kHz and below, but also significantly reduces power consumption, allowing for less stress on the IPG or ETS and enabling prolonged operation. As noted above, excessive power consumption is a serious problem when subsensory therapy is routinely used at higher frequencies. Note Figure 12D The data can also be analyzed based on average charge per second (MSC), as previously described for data from 1 kHz to 10 kHz. Figure 10B ).

[0236] Once determined, information 350 relating to the frequency and pulse width of the optimal subsensory therapy for the absence of sensory abnormalities can be stored in an external device used for programming the IPG 10 or ETS 40, such as the previously described clinician programmer 50 or external controller 45. This is in Figure 13As shown, the control circuitry 70 or 48 of the clinician programmer or external controller is associated with: region information 100i or relational information 98i for frequencies in the range of 1 kHz to 10 kHz, and region information 300i or relational information 310i for frequencies at or below 1 kHz. This information can be stored in memory within the control circuitry or in memory associated with the controller. Storing this information using an external device is useful in assisting clinicians with subsensory optimization, as further described below. Alternatively, and although not shown, information related to frequency and pulse width can be stored in IPG 10 or ETS 40, thus allowing the IPG or ETS to optimize itself without clinician or patient input.

[0237] Information 350 can be incorporated into the fitting module. For example, the fitting module 350 can operate as a software module within the clinician programmer software 66, and may be implemented in the clinician programmer GUI 64. Figure 6 Options can be selected from the advanced menu 88 or mode menu 90. The fitting module 350 can also be operated within the control circuitry of the IPG 10 or ETS 40.

[0238] The fitting module 350 can be used to optimize pulse width when the frequency is known, or vice versa. For example... Figure 13 As shown at the top, a clinician or patient can input a frequency F into the clinician programmer 50 or an external controller 45. This frequency F is passed to the fitting module 350 to determine the pulse width PW for the patient, which is statistically likely to provide adequate pain relief without sensory abnormalities. The frequency F can, for example, be input to relation 98i or 310i to determine the pulse width PW. Alternatively, the frequency can be compared to a relevant region 100i or 300i into which the frequency falls. Once the correct region 100i or 300i is determined, F can be compared with data within that region to determine the pulse width PW, which may be the pulse width between the boundaries of PW+X and PW–X at a given frequency, as previously described. Other stimulation parameters (such as amplitude A, activation electrodes E, their relative percentage X%, and electrode polarity P) can be determined in other ways, such as those described below, to arrive at a complete stimulation procedure (SP) for the patient. Based on data from... Figure 10B The data shows that an amplitude close to 3.0 mA can be used as a logical starting point because this amplitude is shown to be preferred for patients in the 1kHz to 10kHz range. However, other initial starting amplitudes can also be selected, and the amplitude for subsensory therapy can depend on the frequency. Figure 13The top of FIG. 35 shows the use of the fitting module 350 in the opposite manner (i.e., picking the frequency for a given pulse width). Note that in subsequent algorithms, and even in algorithms used outside of any algorithm, in one example, the system can allow the user to associate the frequency and pulse width so that when the frequency or pulse width changes, the other one of the pulse width or frequency is automatically changed to correspond to the optimal setting. In one embodiment, associating the frequency with the pulse width in this manner can comprise an optional feature (e.g., in the GUI 64) that can be used when sub-perception programming is desired, and associating the frequency with the pulse width can not be selected or selectable for use with other stimulation modes.

[0239] Figure 14 An algorithm 355 that can be used to provide sub-perception therapy to SCS patients at frequencies of 10 kHz or less is shown, and some of the steps already discussed above are summarized. Steps 320-328 describe the super-perception sweet spot search. A user (e.g., clinician) selects electrodes to create a bipolar for the patient, for example, by using a GUI of a clinician programmer (320). This bipolar is preferably a symmetric biphasic bipolar and can include virtual bipolars, as previously described.

[0240] The bipolar is transmitted with other stimulation parameters to the IPG or ETS for execution (321) using a telemetry transmitter. Such other stimulation parameters can also be selected in the clinician programmer using the GUI. As a default, the frequency F can equal 90 Hz and the pulse width (PW) can equal 200 microseconds, although this is not strictly necessary and these values can be modified. At this point, if the bipolar provided by the IPG or ETS is not super-perception, i.e., if the patient does not experience paresthesia, the amplitude A or other stimulation parameters can be adjusted to make it so (322). The effectiveness of the bipolar is then gauged by the patient (324) to understand the extent to which the bipolar is covering the patient's pain site. An NRS or other score rating system can be used to determine the effectiveness.

[0241] If the bipolar is not effective, or if it still needs to be searched, a new bipolar can be tried (326). That is, a new electrode can be selected, preferably in a manner that moves the bipolar to a new location along the path 296, as previously described with respect to FIG. 34. The new bipolar is then transmitted to the IPG or ETS for execution (328). Figures 7A-7DThe new dipole can then be transmitted to the IPG or ETS again with the telemetry transmitter (321) and adjusted as necessary to render the dipole super-perception (322). If the dipole is effective, or if the search has been completed and the most effective dipole has been located, the dipole can optionally be modified prior to sub-perception therapy (328). Such modifications as described above can involve selecting other electrodes proximal to the electrodes of the selected dipole to modify the field shape in the tissue to possibly better cover the patient's pain. Thus, the modification of step 328 can change the dipole used during the search to a virtual dipole, or tri-pole, etc.

[0242] Modifications of other stimulation parameters can also occur at this point. For example, the frequency and pulse width can be modified. In one example, a working pulse width can be selected that provides good, comfortable paresthetic coverage (>80%). This can occur by using a frequency of, for example, 200 Hz, and starting with a pulse width of, for example, 120 microseconds. The pulse width can be increased at this frequency until good paresthetic coverage is felt. An amplitude in the range of, for example, 4 to 9 mA can be used.

[0243] At this point, the electrodes (E) selected for stimulation, their polarity (P), and the fraction of the current (X%) they will receive (and possibly the working pulse width) are known and will be used to provide sub-perception therapy. To ensure that sub-perception therapy is provided, the amplitude A of the stimulation is titrated down to a sub-perception, no paresthesia level (330), and transmitted to the IPG or ETS with the telemetry transmitter. As described above, the amplitude A can be set below the amplitude threshold (e.g., 80% of the threshold) where the patient can just begin to feel paresthesias.

[0244] At this point, it can be useful to optimize (332) the frequency and pulse width of the sub-perception therapy being provided to the patient. While the frequency (F) and pulse width (PW) used during the sweet spot search can be used for the sub-perception therapy, it is also beneficial to adjust these parameters to optimal values according to the regions 100i or relationships 98i established at frequencies in the range of 1 kHz to 10 kHz, or the regions 300i or relationships 310i established at frequencies of 1 kHz or below. Such optimization can use the fitting module 350 in Figure 13 Figure 14 ​Option 332a, for example, allows the software in the clinician programmer or IPG or ETS to automatically select the frequency (≤ 10 kHz) and pulse width using region or relationship data relating frequency to pulse width. Option 332a can use the previously determined working pulse width (328) and use the region or relationship to select the frequency. In contrast, option 332b allows the user (clinician) to specify the frequency (≤ 10 kHz) or pulse width (using the GUI of the clinician program). The software can then use the region or relationship again to select the appropriate value for the other parameter (pulse width or frequency (≤ 10 kHz)). In addition, this option can use the previously determined working pulse width to select the appropriate frequency. Option 332c allows the user to enter the frequency (≤ 10 kHz) and pulse width PW, but in a manner that is constrained by the region or relationship. In addition, this option allows the user to enter the working pulse width and frequency appropriate for this working frequency, depending on the region or relationship. The GUI 64 of the clinician programmer can not accept in this example an input of F and PW that does not fall within the region or along the relationship, as such values would not provide optimal sub-perception therapy.

[0245] The frequency or pulse width optimization can occur in other ways that more efficiently search the desired portion of the parameter space. For example, gradient descent, binary search, simplex method, genetic algorithm, etc. can be used for the search. Machine learning algorithms that have been trained using data from patients can also be considered.

[0246] Preferably, when optimizing the frequency (≤ 10 kHz) and pulse width at step 332, these parameters are selected in a manner that reduces power consumption. In this regard, it is preferred to select the lowest frequency, as this will reduce the average charge per second (MCS), reduce the average current drawn from the battery in the IPG or ETS, and thus increase the discharge time, as previously discussed with respect to Figure 10B and Figure 12D Reducing the pulse width, if possible, will also reduce the battery draw and increase the discharge time.

[0247] At this point, all relevant stimulation parameters (E, P, X, I, PW, and F (<10 kHz)) are determined and can be sent from the clinician programmer to the IPG or ETS for execution (334) to provide sub-perception stimulation therapy to the patient. Adjustment (332) of the possibly optimal pulse width and frequency (<10 kHz) can result in these stimulation parameters providing paresthesia. Therefore, the amplitude of the current A can be titrated down again to a sub-perception level (336) if necessary. If necessary, a prescribed sub-perception therapy can be allowed to wash in (338) for a period of time, although as noted previously this can not be necessary because the suprathreshold sweet spot search (320-328) has selected electrodes for a situation where the patient's pain site is well recruited.

[0248] If the sub-perception therapy is ineffective, or adjustment can be used, the algorithm can return to step 332 to select a new frequency (<10 kHz) and / or pulse width according to the previously defined regions or relationships.

[0249] It should be noted that, Figure 14 Not all parts of the steps of the algorithm in FIG. 15 need be performed in actual implementation. For example, if the effective electrodes (i.e., E, P, X) are known, the algorithm can use the information regarding frequency and pulse width to start the sub-perception optimization.

[0250] Figure 15 Another approach is shown in which a fitting module 350 ( Figure 13 ) can be used to determine the optimal sub-perception stimulation for a patient at frequencies of 10 kHz or less. In Figure 15 the fitting module 350 is again incorporated into or used by the algorithm 150, which again can be executed as part of its software on the control circuit of the external device or in the IPG 10. In the algorithm 105, the fitting module 350 is used to pick an initial pulse width for a given particular frequency. However, the algorithm 105 is more comprehensive in that it will test and optimize the amplitude and also optimize the pulse width at different frequencies. As explained further below, the algorithm 105 also optionally helps pick the optimized stimulation parameters that will result in the lowest power requirements of concern to the battery 14 of the IPG. Some of the steps shown in Figure 15 the algorithm 105 are optional, and other steps can also be added. It is assumed that a sweet spot search of the patient has already occurred by the algorithm 105 and the electrodes (E, P, X) have been selected and preferably will remain constant throughout the operation of the algorithm. However, this is not strictly required because these electrode parameters can also be modified as described above.

[0251] Algorithm 105 begins by selecting an initial frequency (e.g., F1) within a range of interest (e.g., ≤10kHz). Algorithm 105 then transmits this frequency to fitting module 350, which selects an initial pulse width PW1 using a previously determined relationship and / or region. For simplicity, in Figure 15 The fitting module 350 is shown as a simple lookup table of pulse width and frequency, which may include another form of information relating to the frequency and pulse width of the stimulus pulses formed to provide pain relief without sensory abnormalities. The selection of pulse width using the fitting module 350 can be more refined, as previously described.

[0252] After selecting the pulse width for a given frequency, the stimulation amplitude A (120) is optimized. Here, multiple amplitudes are selected and applied to the patient. In this example, the selected amplitude preferably uses the optimal amplitude A determined at each frequency (see, for example...). Figure 10B This is determined by the patient's experience over a period of time (e.g., every two days) at amplitudes ranging from A=A2, below (A1), to above (A3). The optimal amplitude among these is chosen by the patient. At this point, further adjustments to the amplitude can be made to test and refine the amplitude to the optimal range for the patient. For example, if A2 is preferred, amplitudes slightly higher (A2+Δ) and slightly lower (A2-Δ) can be tried over a period of time. If a lower value of A1 is preferred, even lower amplitudes (A1-Δ) can be tried. If a higher value of A3 is preferred, even higher amplitudes (A3+Δ) can be tried. Finally, iterative testing of such amplitudes leads to an effective amplitude for the patient that does not cause sensory abnormalities.

[0253] Next, the pulse width can be optimized for the patient (130). Similar to amplitude, this can be achieved by slightly decreasing or increasing the previously selected pulse width (350). For example, at a frequency of F1 and an initial pulse width of PW1, the pulse width can be decreased (PW1-Δ) and increased (PW1+Δ) to see if such a patient-managed setting is preferred. Further iterative adjustments to the amplitude and pulse width can occur at this point, although this is not shown.

[0254] In summary, at a given frequency, an initial pulse width (350) (and preferably also an initial amplitude (120)) is selected for the patient because it is expected that these values ​​will provide effective pain relief without sensory abnormalities. Nevertheless, since each patient is different, the amplitude (120) and pulse width (130) are also adjusted according to the initial values ​​for each patient.

[0255] Thereafter, the optimal stimulation parameters determined for the patient at the tested frequency are stored in the software (135). Optionally, the average charge per second (MCS) of the neurostimulation received by the patient, or other information indicative of power draw (e.g., average Ibat, discharge time) is also calculated and stored. If still other frequencies within the range of interest (e.g., F2) have not been tested, they are tested as described above.

[0256] Once one or more frequencies have been tested, the optimal stimulation parameters previously stored for the patient at each frequency (135) can be used to select stimulation parameters for the patient (140). Because the stimulation parameters at each frequency are suitable for the patient, the selected stimulation parameters can include the stimulation parameters that result in the lowest power draw (e.g., lowest) MSC. This is desirable because these stimulation parameters will be the easiest on the IPG's battery. It can be expected that the stimulation parameters with the lowest MSC determined by the algorithm 105 will include those taken at the lowest frequency. However, each patient is different, and thus this can not be the case. Once the stimulation parameters have been selected, further amplitude optimization (150) can be taken, with the goal of selecting the smallest amplitude that provides sub-perception pain relief without paresthesia.

[0257] It should be noted that the use of the disclosed technology should not necessarily be limited to the particular frequencies tested. Other data suggests that the disclosed technology provides applicability for pain relief without paresthesia at frequencies as low as 2 Hz.

[0258] Various aspects of the disclosed technology include processes that can be implemented in an IPG or ETS, or in an external device such as a clinician programmer or external controller for presenting and operating the GUI 64, which can be expressed in formulas and stored as instructions in a computer readable medium associated with such devices, such as in a magnetic, optical, or solid state memory. The computer readable medium with such stored instructions can also include a device that is readable by a clinician programmer or external controller, such as in a memory stick or removable disk, and can reside elsewhere. For example, the computer readable medium can be associated with a server or any other computer device, thus allowing the instructions to be downloaded to a clinician programmer system or external system or to an IPG or ETS via, for example, the Internet.

Claims

1. A system for programming a spinal cord stimulator (10; 40) having a plurality of electrodes (16) comprising an array (17), comprising: an external system (45; 50) comprising a non-transitory computer readable medium containing instructions that, when executed, allow the external system to: provide a plurality of different first sets of stimulation parameters to the spinal cord stimulator (10; 40), wherein each first set of stimulation parameters causes the spinal cord stimulator to form a biphasic test pulse at at least two of the electrodes (16), wherein the biphasic test pulse is formed at 130 Hz or lower, wherein each biphasic test pulse comprises a first phase having a first polarity and a second phase having a second polarity opposite the first polarity, wherein both the first pulse phase and the second pulse phase are actively driven by stimulation circuitry in the spinal cord stimulator (10; 40), and wherein each first set of stimulation parameters causes suprathreshold stimulation to occur at different locations relative to the array (17); wherein, after determining a set of first stimulation parameters that treats a pain symptom in a patient, the determined first set of stimulation parameters corresponds to a treatment location relative to the array (17), the instructions, when executed, further allow the external system (45; 50) to: provide a second set of stimulation parameters to the spinal cord stimulator (10; 40) for causing the spinal cord stimulator to form a treatment pulse at at least two of the electrodes (15), wherein the treatment pulse is formed at 130 Hz or lower, wherein the second set of stimulation parameters causes subthreshold stimulation to occur at the treatment location.

2. The system of claim 1, wherein, the biphasic test pulse and the treatment pulse are the same frequency.

3. The system of claim 1 or 2, wherein, the charge of the first phase is equal to the charge of the second phase.

4. The system of claim 1, wherein, the biphasic test pulse comprises a symmetric biphasic pulse, wherein the duration of the first phase is equal to the duration of the second phase, and wherein the amplitude of the first phase is equal to the amplitude of the second phase but has a polarity opposite the amplitude of the second phase.

5. The system of claim 1, wherein, the non-transitory computer readable medium is configured to determine the second set of stimulation parameters by adjusting at least one of the stimulation parameters of the determined first set of stimulation parameters without adjusting the treatment location relative to the array.

6. The system of claim 1, wherein, the determined first set of stimulation parameters comprises a set of stimulation parameters with which the patient responds favorably to treatment of the pain symptom.

7. The system of claim 1, wherein, each first set of stimulation parameters causes suprathreshold stimulation to occur as a bipolar at different locations.

8. The system of claim 1, wherein, the second stimulation parameters cause subthreshold stimulation to occur as a bipolar at the treatment location.

9. The system of claim 1, wherein, the determined first set of stimulation parameters is determined by using feedback from the patient.

10. The system of claim 1, wherein, the determined first set of stimulation parameters comprises an amplitude of the test pulse, and wherein the second set of stimulation parameters comprises an amplitude of the treatment pulse, and wherein the amplitude of the treatment pulse is lower than the amplitude of the test pulse.

11. The system of claim 10, wherein, the determined first set of stimulation parameters differs from the second set of stimulation parameters only in the amplitude of the test pulse versus the treatment pulse.

12. The system of claim 1, wherein, The second set of stimulation parameters includes a frequency and a pulse width of the therapy pulses, and wherein at least one of the frequency and the pulse width is selected by the computer readable medium to cause sub-perception stimulation to occur.

13. The system of claim 12, wherein, The frequency and the pulse width are selected by the computer readable medium based on information relating to a frequency and a pulse width that forms the therapy pulses to cause sub-perception stimulation to occur at the therapy location.

14. The system of claim 1, wherein, The computer readable medium includes instructions that, when executed, allow the external system to direct current between the plurality of electrodes to adjust the therapy location to a new therapy location relative to the array.

15. The system of claim 1, wherein, The computer readable medium further includes instructions that, when executed, allow the external system to program the spinal cord stimulator during the programming session, and wherein the instructions are configured to ramp in the therapy pulses over a period of one hour or less during the programming session to cause the sub-perception stimulation to occur at the therapy location.

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